Layered network node, network incorporating the same, node, and layered network

ABSTRACT

A layered network node of which a network it belongs is divided up into cells which are constituted by a plurality of nodes; the cells are defined as virtual nodes; if links exist which connect the interiors of the virtual nodes and the exterior, contact points between them are defined as interfaces of the virtual nodes; the virtual network constituted by the virtual nodes is further divided up into cells and making them into virtual nodes; said virtual network is defined as a network of a higher level with respect to the initial virtual network; by performing said operation of division into cells and making into virtual nodes once or a plurality of times, the layered network is constituted; path computation is performed from the source node to a destination node in a stepwise manner by dispersing it over the various layers.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to construction technology for apath networks which conduct traffic engineering such as route selectionand rearrangement of paths. In particular, the present invention relatesto a layered network node, a network incorporating the same, a node, anda layered network.

[0003] Priority is claimed on Japanese Patent Application No.2002-293679 filed on Oct. 7, 2002 and Japanese Patent Application No.2003-036801 filed on Feb. 14, 2003, the contents of which areincorporated herein by reference.

[0004] 2. Description of Related Art

[0005] In the case of networks in which plural layers are intermixedwith each other, network management for each layer is often conducted ineach layer individually. The network management differs depending on thelayer, and there may be mentioned a central-control method in which oneapparatus monitors all conditions of the network and controls, and adistributed-control method in which all nodes in the network shareinformation by exchanging the link state. In addition to these, limitingonly one layer control, there is a method which divides a network intoplural areas, and manages the areas individually.

[0006] In the case of conducting distributed-control multi-layer trafficengineering under conditions in which networks of plural layers areintermixed with each other, conventionally, traffic engineering wasconducted for the entire network (see, for example, the followingdocuments No. 1 and No. 2). Therefore, there are problems in that alarge scale network is enlarged because the information content which isgenerally treated using routing protocol is represented by OPSF (OpenShortest Path First), etc. Document No. 1

[0007] K. Sato, N. Yamanaka, et al., “GMPLS-based photonic multilayerrouter (Hikari router) architecture: an overview of traffic engineeringand signaling technology,” IEEE Commun. Mag., Vol. 40, Issue 3, Mar.2002 Document No. 2

[0008] E. Oki, N. Yamanaka, et al., “A heuristic multi-layer optimumtopology design scheme based on traffic measurement for IP+photonicnetworks,” Optical Fiber Communication Conference and Exhibit, pp.17-22, March 2002

[0009] This problem will be explained in more detail. FIG. 62 shows anetwork being comprised by plural network layers. In this example, thenetwork is comprised by an IP layer and a TDM (Time Division Multiplex)layer and a wavelength layer. In this network, each node advertises alink state which is composed from a IP address, a maximum broad band, aband for use, and so on.

[0010] A node for setting paths sets paths by conducting calculationbased on this link stage whether a TDM path and a Lambda path are to benewly set or not. Also, the node for setting paths sets paths byconducting calculations based on the link stage to find which path willprovide minimum cost. In the case of conducting rearrangement of a routeof some IP path, at the same time, a calculation is performed to findnecessity of rearrangement of a Lambda path in a lower level. In thiskind of network, along with enlargement of the network scale, processload such as advertisement volume of link states, calculation amount ofroute computation, etc., increases. Therefore, scale ability cannot bemaintained at some constant scale. The same thing can be said concerningincrement of layer to be treated generally.

SUMMARY OF THE INVENTION

[0011] The present invention is made in view of the above and an objectthereof is to provide a layered network node, a network, layered routeselection method, a program, and a recording medium which can realizeenlargement to a large scaled network, and moreover, which can avoidineffective calculation by identifying areas of layers which need routecomputation, and thus, route computation can be conducted effectively.

[0012] Also, the present invention has an object to provide a node, alayered network, a network control apparatus, and a construction methodof a layered network which can realize enlargement to a large scalenetwork even though the network requires complicated processes asmultilayer network, and moreover, which can avoid ineffectivecalculation by identifying areas of layers which need route computation,and thus, route computation can be conducted effectively.

[0013] [Layered Network Node]

[0014] The layered network node according to the present invention andthe network which incorporates it perform path computation from thesource node to the destination node by dispersing it over the variouslayers in a stepwise manner. In this case, it is possible to implementexpansion of the scale of a large scale network, since it is possible tokeep the amount of computation upon each of the layers small, incomparison with a prior art example in which traffic engineering isperformed for the network as a whole. Furthermore, since it is possibleto perform the computation after having specified the range of layersover which path computation is to be required, it is possible toeliminate computation which would be inefficient, and it is possible toperform the path computation at high efficiency.

[0015] A first aspect of the present invention is a node which isprovided in a network consisting of one or a plurality of layers,comprising: a means for mutually interchanging with other nodesinformation about the present node and links which are connected to thepresent node (hereinafter termed “link state information); a means forstoring link state information for one or for all of the nodes withinsaid network which has been obtained by this interchanging means; ameans for selecting a path for an LSP of one or a plurality of types oflayer, based upon link state information which has been stored in saidstoring means according to an LSP establishment request; and a means forchanging the path which has been selected and established by thisselection means, according to an LSP change request, based upon linkstate information which has been stored in said storing means.

[0016] In the above, it is desirable for the present invention for thenetwork to which said node belongs to be a layered network which isbuilt up by: dividing up into cells which are constituted by a pluralityof nodes; defining these cells as virtual nodes; if links exist whichconnect the interiors of the virtual nodes and the exterior, definingthe contact points between these interiors of the virtual nodes and theexterior as interfaces of the virtual nodes; further dividing up thevirtual network which has been constituted by the virtual nodes intocells; making them into virtual nodes; further dividing them up intocells; the virtual network which has been made into virtual nodes isdefined as a network of a higher level with respect to the initialvirtual network; and by performing the above described operation ofdivision into cells and making into virtual nodes once or a plurality oftimes; and to comprise a link state database which accumulates linkstate information which is advertised from other nodes within thevirtual node to which self node belongs or from other virtual nodes;with the nodes which fulfill a function of interfacing with nodes withinthe virtual node or with the exterior of the virtual node being definedas border nodes, and comprising: a link state abstraction sectioncomprising a means for, when the present node is positioned at selfborder node, creating interface information for the exterior of thevirtual node based upon link state information interior to the virtualnode; and an advertisement section which advertises said interfaceinformation which has been created to the exterior of the virtual node.The node of the present invention will be termed a layered network node.

[0017] When this type of layered structure is defined, it becomesunnecessary to perform computation for the entire network all together,and it is possible to implement expansion of the scale of a large scalenetwork, since it is possible to perform the computation for each of thehierarchical layers.

[0018] It is desirable for there to be further included a means forrecognizing a link group, among a plurality of links which mutuallyconnect virtual nodes together, which connects between the same virtualnode; and a processing means for treating the links which are includedwithin the link group which has been recognized by this recognitionmeans as a single virtual link.

[0019] In this case, one of the virtual links can be constituted by asingle optical LSP which is WDM (Wavelength Division Multiplexed).

[0020] Or alternatively, it is desirable for there to be furtherincluded: a means for recognizing a first link group, among a pluralityof which mutually connect virtual nodes together, which connects betweenthe same virtual node; a means for further classifying the first linkgroup which has been recognized by said recognition means into secondlink groups which possess the same switching capability; and aprocessing means for treating the links which are included within thesecond link group which has been classified by said classification meansas a single virtual link.

[0021] In this case, the virtual links with the same switchingcapability are defined in common, and it is possible to enhance theutilization efficiency of the hardware by allotting one of the opticalLSPs which has, for example, been wavelength multiplexed (WDM) by unitsof switching capability.

[0022] The link state abstraction section may comprise a switchingcapability allotment means for performing allotment of the switchingcapability within the virtual node to which the present node belongs bya link which is connected to the present node to a link whichcorresponds to an interface which connects the virtual node and moreoverto which the present node belongs and the exterior; and said interfaceinformation may be information about the switching capability which hasbeen allotted to said interfaces by said switching capability allotmentmeans.

[0023] In other words, by taking the information as to which switchingcapability is allotted to which link as interface information, in eachvirtual node, it is possible to ascertain the mutual connectionrelationships between the virtual nodes by units of switchingcapability.

[0024] Or, the link state abstraction section may comprise a switchingcapability allotment means for performing allotment of the switchingcapability within the virtual node to which the present node belongs bya link which is connected to the present node to a link whichcorresponds to an interface which connects the virtual node and moreoverto which the present node belongs and the exterior; and a cost allotmentmeans for allotting a transmission cost to each switching capabilitywhich has been allotted by said switching capability allotment means;and said interface information may be information about the switchingcapability which has been allotted to said interfaces by said switchingcapability allotment means, and information about the transmission costswhich have been allocated to the switching capabilities of saidinterfaces by said cost allotment means.

[0025] In this case, along with the mutual connection relationshipsbetween the virtual nodes, it is also possible to ascertain thetransmission cost when utilizing the link. Due to this, it is not thepath for which the physical distance is the shortest which is simplytaken as the shortest path; rather, it is possible to take the path forwhich the transmission cost is the least as the shortest path.

[0026] It is desirable for the information about the switchingcapability which has been allotted to said interfaces to be created incorrespondence with each layer of an LSP which can be establishedbetween the present node as a border node or a virtual border node, andanother border node or another virtual border node which belongs withinthe same virtual node.

[0027] In this case, it is possible to obtain information for each layerindividually, and, since the path computation is performed for eachlayer individually, the utilization level is high.

[0028] The information about the switching capability which has beenallotted to said interfaces may be information which is related to theswitching capability of a border node or a virtual border node to whichthe link which constitutes said interface is directly connected.

[0029] It is desirable for said advertisement section to comprise ameans for performing an advertisement to the exterior of the virtualnode each time a change in switching capability of said border nodeoccurs, or for said advertisement section to comprise a means forperforming an advertisement to the exterior of the virtual node at afixed interval. In this case, it is possible to obtain the newestinformation for each of the virtual nodes. It should be understood that,in the case of performing advertisement to the exterior of the virtualnode at a fixed interval, it is often the case that the burden ofadvertisements is reduced, as compared with the case of performingadvertisement to the exterior of the virtual node each time a changeoccurs in the switching capability.

[0030] The information about transmission cost may be generated as thereciprocal of the total number of interfaces which are not in use towhich switching capability of said layer which is included in thevirtual node is allotted.

[0031] In other words, the greater is the total number of interfaceswhich are not in use, the smaller is the transmission cost, since thegreater does the available room for reception by the interfaces become.

[0032] Or, alternatively, the information about transmission cost may begenerated, in relation to the number of interfaces to which switchingcapability of said layer which is included in the virtual node isallotted which are in use, and the total number of interfaces, as thenumber of interfaces in use divided by the total number of interfaces.

[0033] In other words, the smaller is the number of interfaces which arein use with respect to the total number of interfaces, the smaller isthe transmission cost, since the greater does the available room forreception by the interfaces become.

[0034] It is desirable for said information about transmission cost,between a border node within the virtual node and another border nodewhich belongs to the same border node as said border node, to beinformation which is determined for each layer of the LSP which isestablished as the cost when establishing a LSP of any layer.

[0035] In this case, it is possible to obtain information for each layerindividually, and, since the path computation is performed for eachlayer individually, the utilization level is high.

[0036] It is desirable for said cost allotment means, for example, tocomprise a means for calculating a cost value of the path for which thevalue, which is obtained by adding, along the path when establishing anLSP between a border node within the virtual node and another bordernode which belongs to the same border node as said border node, the linkcost of the link and the node cost of the node or the virtual node,becomes minimum.

[0037] In this case, it is possible to select a path for which the costis minimum by taking both the link cost and the node cost into account.

[0038] Or, it is desirable for said cost, for example, to be the valuewhich is obtained by adding the link cost of the link and the node costof the node or the virtual node along the path of the minimum number ofhops which is established between a border node within the virtual nodeand another border node which belongs to the same border node as saidborder node; and for there to be comprised a means for, if there existsa plurality of said paths of the minimum number of hops, selecting fromamong cost value candidates which are aggregates of a plurality ofvalues which are obtained by said addition, as the cost value, that onefor which its value becomes minimum.

[0039] In this case, it is possible to select a path for which the costis minimum by taking both the link cost and the node cost into account,and also according to the minimum number of hops.

[0040] The value which is obtained by said addition, for example, may bethe reciprocal of the number of interfaces which are not in use to whichswitching capability of said layer which is included in the virtualnodes along said path is allotted.

[0041] In other words, the greater is the number of interfaces which arenot in use, the smaller is the value which is obtained by said addition,since the greater does the available room for reception of saidinterfaces become. As has already been explained, the difference betweenthe transmission cost and the value which is obtained by said additionis that, while the transmission cost is a value which has beendetermined in advance for each link, on the other hand, the value whichis obtained by said addition is a value which is calculated according tothe path.

[0042] Or, said value which is obtained by said addition may be given,for example, in relation to the number of interfaces to which switchingcapability of said layer which is included in the nodes along said pathis allotted which are in use, and the total number of interfaces, by thenumber of interfaces used divided by the total number of interfaces.

[0043] In other words, the smaller is the number of interfaces which arein use with respect to the total number of interfaces, the smaller doesthe value which is obtained by said addition become, since the greateris the amount of room available for reception of the interfaces.

[0044] It is desirable for a node which corresponds to an interface of avirtual node to comprise a means for computing information about saidtransmission cost, or said cost, at a time interval which is fixed inadvance, based upon said link state information; or for a node whichcorresponds to an interface of a virtual node to comprise a means forcomputing information about said transmission cost, or said cost, basedupon said link state information, whenever change of the utilizationstate of the interface within the virtual node is notified byadvertisement of link state information and the utilization state of theinterface changes. In this case, each of the virtual nodes is able toobtain the newest information. It is often the case that the burden ofcomputation when the computation is performed at a fixed time intervalis lower, as compared with the case when the computation is performedeach time a change in the utilization state of the interfaces takesplace.

[0045] [Network Comprising a Layered Network Node]

[0046] A second aspect of the present invention is a network whichcomprises a layered network node according to the present invention.

[0047] [Layered Path Selection Method]

[0048] A third aspect of the present invention is a layered pathselection method when establishing an LSP of any layer within a networkwhich comprises a layered network node according to the presentinvention, in which procedures are executed of: when selecting a pathfrom a source node to a destination node, deciding, by referring to saidlink state database of the lowest level 1, whether or not, among saidvirtual nodes of level 1, the destination node is present within avirtual node which includes the source node; if the source node and thedestination node are not present within the same virtual node, deciding,by referring to said link state database of the next higher level 2,whether or not the destination node is present within a virtual node ofsaid level 2 which includes the source node; by repeating this decisionuntil the source node and the destination node are included within thesame virtual node, selecting a virtual node of a level N (where N is anatural number) which includes both the source node and the destinationnode; when selecting a path of level N from the source node to thedestination node within self virtual node of level N which has beenselected, selecting the path selection of a virtual node group which isincluded within said virtual node of level N which has been selected bysaid selection means of said level N based upon said link state databaseof level N; when further selecting a path of the next lowest level (N-1)from the source node to the destination node from among the virtualnodes which are included in this path of level N which has beenselected, selecting by said selection means of said level (N-1) basedupon said link state database of the next lowest level (N-1) than saidvirtual node which has been selected; and by repeating this until thelowest level 1, selecting a path from the source node to the destinationnode.

[0049] In this case, a level which includes both the source node and thedestination node is searched for, and an upper limit for the level isspecified. Due to this, there is no object for path computation atlevels higher than this one, and so it is possible to eliminatecomputation which will be useless. By doing this, the path computationis performed for each level individually by searching in order from thetopmost level towards the lower levels. In this case, it is possible toimplement increase of the scale of a large scale network, since theamount of computation is limited for each of the levels even if thescale of the network is increased.

[0050] Or alternatively, the third aspect of the present invention is alayered path selection method when establishing an LSP of any layerwithin a network which comprises a layered network node according to thepresent invention, in which procedures are executed of: when selecting apath from a source node to a destination node, in a network which ismade up from virtual nodes of a topmost level N, deciding, by referringto said link state database of said level N, whether or not the sourcenode and the destination node are present within the same virtual node;if the source node and the destination node are present within the samevirtual node, deciding, by referring to said link state database of thenext lower level (N-1) within self virtual node, whether or not thesource node and the destination node are present within the same virtualnode in the network of the next lower level (N-1) within self virtualnode; selecting a virtual node of the level (N-k) which includes boththe source node and the destination node, by repeating this decisionuntil the source node and the destination node are included withindifferent virtual nodes, and selecting the virtual node of the nexthighest level (N-k) thereto (where k is a natural number); whenselecting a path of level (N-k) from the source node to the destinationnode within self virtual node, selecting the path selection of a virtualnode group which is included within said virtual node of level (N-k)which has been selected by said selection means of said level (N-k)based upon said link state database of said level (N-k); when furtherselecting a path of the next lowest level (N-k-1) from the source nodeto the destination node from among the virtual nodes which are includedin this path of level (N-k) which has been selected, selecting by saidselection means of said level (N-k-1) based upon said link statedatabase of the next lowest level (N-k-1) than said virtual node whichhas been selected; and by repeating this until the lowest level 1,selecting a path from the source node to the destination node.

[0051] To compare the former method with the latter method, theprocedures for searching for the level which includes both the sourcenode and the destination node are different. With the former method, thesearch is performed in the direction from the lower levels in ordertowards the higher levels, while, with the latter method, the search isperformed in the direction from the higher levels in order towards thelower levels.

[0052] For a virtual node of a lower level than the level which includesboth said source node and said destination node, the computation forselecting the path within the present node may be performed by thatborder node, among the border nodes which are included within selfvirtual node, which is allotted as an input-output interface of saidpath.

[0053] Or, for a virtual node of a lower level than the level whichincludes both said source node and said destination node, thecomputation for selecting the path within the present node may beperformed by that border node, among the border nodes which are includedwithin self virtual node, which is determined in advance as arepresentative node.

[0054] As has been described above, it is possible to execute thecomputation procedure with high efficiency by determining the nodes forwhich the path computation is to be performed in advance. Furthermore,in the latter case, it is possible to reduce the tendency of the burdenof the computation by shifting the node in order, each time one episodeof computation of a representative node is completed.

[0055] [Program]

[0056] A fourth aspect of the present invention is a program which, bybeing installed upon an information processing device, causes saidinformation processing device, when establishing an LSP of any layerwithin a network which comprises said layered network node, to executeprocedures of: when selecting a path from a source node to a destinationnode, deciding, by referring to said link state database of the lowestlevel 1, whether or not, among said virtual nodes of level 1, thedestination node is present within a virtual node which includes thesource node; if the source node and the destination node are not presentwithin the same virtual node, deciding, by referring to said link statedatabase of the next higher level 2, whether or not the destination nodeis present within a virtual node of said level 2 which includes thesource node; by repeating this decision until the source node and thedestination node are included within the same virtual node, selecting avirtual node of a level N (where N is a natural number) which includesboth the source node and the destination node; when selecting a path oflevel N from the source node to the destination node within self virtualnode of level N which has been selected, selecting the path selection ofa virtual node group which is included within said virtual node of levelN which has been selected by said selection means of said level N basedupon said link state database of level N; when further selecting a pathof the next lowest level (N-1) from the source node to the destinationnode from among the virtual nodes which are included in this path oflevel N which has been selected, selecting by said selection means ofsaid level (N-1) based upon said link state database of the next lowestlevel (N-1) than said virtual node which has been selected; and, byrepeating this until the lowest level 1, selecting a path from thesource node to the destination node.

[0057] Or, the fourth aspect of the present invention is a programwhich, by being installed upon an information processing device, causessaid information processing device, when establishing an LSP of anylayer within a network which comprises a layered network node accordingto claim 1, to execute procedures of: when selecting a path from asource node to a destination node, in a network which is made up fromvirtual nodes of a topmost level N, deciding, by referring to said linkstate database of said level N, whether or not the source node and thedestination node are present within the same virtual node; if the sourcenode and the destination node are present within the same virtual node,deciding, by referring to said link state database of the next lowerlevel (N-1) within self virtual node, whether or not the source node andthe destination node are present within the same virtual node in thenetwork of the next lower level (N-1) within self virtual node;selecting a virtual node of the level (N-k) which includes both thesource node and the destination node, by repeating this decision untilthe source node and the destination node are included within differentvirtual nodes, and selecting the virtual node of the next highest level(N-k) thereto (where k is a natural number); when selecting a path oflevel (N-k) from the source node to the destination node within selfvirtual node, selecting the path selection of a virtual node group whichis included within said virtual node of level (N-k) which has beenselected by said selection means of said level (N-k) based upon saidlink state database of said level (N-k); when further selecting a pathof the next lowest level (N-k-1) from the source node to the destinationnode from among the virtual nodes which are included in this path oflevel (N-k) which has been selected, selecting by said selection meansof said level (N-k-1) based upon said link state database of the nextlowest level (N-k-1) than said virtual node which has been selected; andby repeating this until the lowest level 1, selecting a path from thesource node to the destination node.

[0058] [Recording Medium]

[0059] A fifth aspect of the present invention is a recording mediumwhich can be read in by said information processing device, upon whichis recorded a program according to the present invention. By recordingthe program of the present invention upon a recording medium, it ispossible to install the program of the present invention upon saidinformation processing device by using this recording medium. Or, it ispossible to install the program of this preferred embodiment directlyupon said information processing device via a network from a server uponwhich the program of the present invention is stored.

[0060] In this case, it is possible to implement extension of a largescale network by utilizing an information processing device such as acomputer device, and, furthermore, since it is possible to perform thecomputation after having specified a range of layers upon which it isconsidered to be necessary to perform path computation, it is possibleto eliminate computation which would be useless, and it is possible toimplement a layered network node, a network, and a layered pathselection method which can perform path computation at good efficiency.

[0061] As has been explained above, according to the layered networknode and the network incorporating such a node according to the presentinvention, it is possible to implement increase of the scale of a largescale network. Furthermore, since it is possible to perform thecomputation after having specified a range of layers for which it isnecessary to perform path computation, it is possible to eliminatecomputation which would become useless, and it is possible to performpath computation at high efficiency.

[0062] [Node, and Layered Network]

[0063] For a network in which the processing burden of the volume oflink state advertisements, the amount of computation for the pathcomputation, and so on is very great when the entire network is handledall together as a whole, with the node and the layered network accordingto the present invention, by introducing the general concept of avirtual node as explained below, dispersing processing of the processingburden of the network as a whole is performed by layering these virtualnodes, and by thus performing dispersal of the processing over thevarious virtual nodes.

[0064] In this case, it is possible to implement increase of the scaleof the network even in the case of a network in which the processingburden of the network as a whole is very great. Since it is possible toperform the path computation after having specified the range over whichsaid path computation is required, accordingly it is possible to performthe path computation with good efficiency.

[0065] [Node]

[0066] In other words, a sixth aspect of the present invention is a nodewhich constitutes a virtual node of level 1 in a layered network whichhas been defined by dividing up the nodes which make up the network intocells each made up from one or a plurality of said nodes and definingthese cells as virtual nodes of level 1, so that these virtual nodes oflevel 1 constitute a virtual network of level 1, further dividing upthese virtual nodes of level 1 which constitute said virtual network oflevel 1 into cells which are constituted by one or a plurality ofvirtual nodes, so as to constitute virtual nodes of level 2, andconstituting a layered network by virtual networks of levels 1 through Nwhich have been built up by performing the process of dividing intocells and making into virtual nodes in this manner once or a plurality Nof times, and by, if a link exists in said layered network whichconnects between different virtual nodes of the same level or ofdifferent levels, defining a node which corresponds to the point ofcontact between the interior of the virtual node upon this link and theexterior as an interface, so that, when the highest level virtual nodeto which said interface is related is of level M (where MAN), saidinterface serves as a plurality of hierarchical interfaces of level 1through level M; and is a node which does not correspond to saidinterface.

[0067] In the above description, it is desirable for the presentinvention to include a means for advertising to an other node withinself virtual node link information about a link which has been connectedto self node and link cost information for said link; a means forreceiving, from an other node within self virtual node, saidadvertisement of link information within self virtual node and link costinformation for said link, and storing said information; and a means forreceiving, from a node which corresponds to said interface within selfvirtual node, said advertisement of link information between said nodeand a node which corresponds to an interface with a virtual node oflevel 2 or greater, and link cost information for said link, and storingsaid information.

[0068] In this case, each node is able to store link information andlink cost information for within self virtual node and also linkinformation and link cost information between border nodes of othervirtual nodes, so that it is possible to perform path computation basedupon this information.

[0069] It is desirable for there to be further included a means fortransmitting its own IP address to a node which corresponds to aninterface of self virtual node; and a means for storing external IPaddress group information, which is information about an IP address ofan other node which belongs to a virtual node other than self virtualnode, and about the virtual node to which said IP address belongs, whichhave been transmitted from the node which corresponds to said interface.In this case, each node is able to be aware of the position of the nodewhich it should take as its destination.

[0070] It is possible further to include a means for transmitting itsown IP address to a node which corresponds to an interface of selfvirtual node; and a means for requesting and obtaining, from the nodewhich corresponds to said interface, external IP address groupinformation, which is information about an IP address of an other nodewhich belongs to a virtual node other than self virtual node, and aboutthe virtual node to which said IP address belongs.

[0071] In this case, each of the nodes is able, without storing the IPaddress group information, to receive offers of the IP address groupinformation from the node which corresponds to the interface, accordingto requirements. Accordingly, it is possible to reduce the amount ofdata for each node.

[0072] It is possible further to include a means for transmitting itsown IP address and link cost information between itself and a node whichcorresponds to an interface with self virtual node to the node whichcorresponds to said interface; and a means for storing external IPaddress group information, which is information about an IP address ofan other node which belongs to a virtual node other than self virtualnode, and about the virtual node to which said IP address belongs, whichhas been transmitted from the node which corresponds to said interface,and link cost information from the node which corresponds to saidinterface to said other node, in correspondence to the IP address ofsaid other node. In this case, it is possible for each node to be awareof the position of the node which it should take as its destination, andof the link cost to said node.

[0073] It is also possible further to include a means for transmittingits own IP address and link cost information between itself and a nodewhich corresponds to an interface with self virtual node to the nodewhich corresponds to said interface; and a means for requesting andobtaining, from the node which corresponds to said interface, designatesthe IP address of said other node, external IP address groupinformation, which is information about an IP address of an other nodewhich belongs to a virtual node other than self virtual node, and aboutthe virtual node to which said IP address belongs, and link costinformation from the node which corresponds to said interface to saidother node.

[0074] In this case, each node is able, without storing the IP addressgroup information and the link cost information, to receive offers ofthe IP address group information from the node which corresponds to theinterface, according to requirements. Accordingly, it is possible toreduce the amount of data for each node.

[0075] It is desirable to include a means for dispatching a packet forchecking reachability to the node which corresponds to said interface ofself virtual node. In this case, the node which corresponds to theinterface is able to obtain information about reachability which isrelated to the other nodes.

[0076] It is also possible to include a means for computing respectivelink costs for nodes which correspond to a plurality of said interfacesof said virtual node, and for said dispatching means to include a meansfor dispatching a packet for checking reachability to the node whichcorresponds to said interface for which the link cost is the least,according to the results of computation by this computation means. Inthis case, the node which corresponds to the interface is able to obtaininformation about reachability which is related to the other nodes forwhich the link cost is the least.

[0077] It is also possible to include a means for computing respectivelink costs for nodes which correspond to a plurality of said interfacesof said virtual node, and for said dispatching means to include a meansfor dispatching packets for checking reachability to the nodes whichcorrespond to said interfaces for which the link cost, according to theresults of computation by this computation means, is the smallest inorder until the nth, where n is a natural number. In this case, the nodewhich corresponds to the interface is able to obtain information aboutreachability which is related to the other nodes for which the link costis up to the n-th least.

[0078] It is possible to include a means for computing respective linkcosts for nodes which correspond to a plurality of said interfaces ofsaid virtual node, and for said dispatching means to include a means fordispatching packets for checking reachability to the nodes whichcorrespond to said interfaces for which the link cost, according to theresults of computation by this computation means, is the smallest inorder until the nth (where n is a natural number), said packetsincluding information about said order.

[0079] In this case, the node which corresponds to the interface is ableto obtain information which becomes a criterion of the reachability andthe link cost which are related to the other node for which the linkcost is the n-th least. This information which becomes a criterion canbe implemented with an extremely small amount of data, as compared withthe case of link cost information which has not been modified.

[0080] Or, it is possible to incorporate a means for advertising linkinformation about a link which has been connected to self node to another node within self virtual node and link cost information for saidlink; and a means for receiving said advertisement of link informationwithin self virtual node and link cost information for said link from another node within self virtual node, and storing said information.

[0081] In this case, the information which is stored by the node islimited to the information within self virtual node. Accordingly, it ispossible to reduce the amount of data for the node. However, with onlythe information for within self virtual node, it is not possible toperform path computation which extends to other virtual nodes.

[0082] Here, it is desirable to incorporate a means for, ahead of pathcomputation, requesting and obtaining, from said node which correspondsto said interface, link information between a node which corresponds tothe interface with self virtual node and a node which corresponds to aninterface with a virtual node of level 2 or higher, and link costinformation for said link.

[0083] In this case it is possible for the node to store the minimumnecessary amount of data, since it is possible to obtain informationfrom the node which corresponds to the interface, according to therequirements for path computation.

[0084] A seventh aspect of the present invention is a node whichcorresponds to said interface, and which comprises a means foradvertising to an other node within self virtual node link informationabout a link within self virtual node which has been connected to selfnode and link cost information for said link, and link information for alink with a node which corresponds to an interface of another virtualnode which has been connected to self node, and link cost informationfor said link; a means for receiving said advertisement of linkinformation within self virtual node and link cost information for saidlink from an other node within self virtual node, and storing saidinformation; and a means for receiving, from a node which corresponds tosaid interface with another virtual node, advertisement of linkinformation with a node which corresponds to said interface of a higherlevel, and link cost information for said link, and storing saidinformation.

[0085] By the node which corresponds to the interface advertising toother nodes within self virtual node, it is possible for the nodes toobtain the link information and the link cost information.

[0086] It is desirable for there to be further included: a means forgathering together and storing IP address information from other nodeswithin self virtual node; a means for advertising the IP addressinformation which has been gathered together by this gathering togetherand storing means to a node which corresponds to an interface of anothervirtual node; and a means for storing external IP address information,which is information about the IP address of another node which belongsto a virtual node other than self virtual node and about the virtualnode to which said IP address belongs, and which has been advertisedfrom the node which corresponds to the interface of the other virtualnode, and transmitting it to another node within self virtual node.

[0087] It is possible for the nodes to obtain information aboutreachability by the node which corresponds to the interface advertisingto the other nodes within self virtual node. There may be incorporated ameans for gathering together and storing IP address information fromother nodes within self virtual node; a means for advertising the IPaddress information which has been gathered together by this gatheringtogether and storing means to a node which corresponds to an interfaceof another virtual node; a means for storing external IP addressinformation, which is information about the IP address of another nodewhich belongs to a virtual node other than self virtual node and aboutthe virtual node to which said IP address belongs, and which has beenadvertised from the node which corresponds to the interface of the othervirtual node; and a means for offering the external IP address groupinformation which has been stored in said storing means to said othernodes, according to requests from said other nodes.

[0088] By the node which corresponds to the interface offering theexternal address group information according to requests from the othernodes, said other nodes need only to store the minimum amount ofinformation which is required, since said other nodes are able to obtainexternal address group information according to requirements.

[0089] It is possible to incorporate a means for gathering together andstoring IP address information from other nodes within self virtualnode, and link cost information between said other nodes and self node;a means for advertising the IP address information and link costinformation which have been gathered together by this gathering togetherand storing means to a node which corresponds to an interface of anothervirtual node; and a means for storing external IP address information,which is information about the IP address of another node which belongsto a virtual node other than self virtual node and about the virtualnode to which said IP address belongs, and which has been advertisedfrom the node which corresponds to the interface of the other virtualnode, and link cost information from said node which corresponds to theinterface of the other virtual node to said other node, incorrespondence to the IP address of said other node, and transmitting itto another node within self virtual node.

[0090] By the node which corresponds to the interface transmitting theexternal address group information and the link cost information toother nodes within self virtual node, it is possible for the nodes toobtain the external address group information and the link costinformation.

[0091] It is possible to incorporate a means for gathering together andstoring IP address information from other nodes within self virtualnode, and link cost information between said other nodes and self node;a means for advertising the IP address information and link costinformation which have been gathered together by this gathering togetherand storing means to a node which corresponds to an interface of anothervirtual node; a means for storing external IP address information, whichis information about the IP address of another node which belongs to avirtual node other than self virtual node and about the virtual node towhich said IP address belongs, and which has been advertised from thenode which corresponds to the interface of the other virtual node, andlink cost information from said node which corresponds to the interfaceof the other virtual node to said other node, in correspondence to saidIP address of said other node; and a means for offering the external IPaddress group information and the link cost information which have beenstored in said storing means to said other nodes, according to requestsfrom said other nodes.

[0092] By the node which corresponds to the interface offering theexternal address group information and the link cost informationaccording to the requests from other nodes, it is possible for saidother nodes to obtain the external address group information and thelink cost information according to requirements, and accordingly it ispossible for said other nodes to store the minimum amount of informationwhich is required.

[0093] It is possible to incorporate: a means for receiving a packet forchecking reachability from an other node within self virtual node; ameans for summarizing the IP addresses of packets which have beenreceived by said receiving means and generating internal address groupinformation which is related to a node within self virtual node; a meansfor interchanging and harmonizing the internal IP address groupinformation which has been generated by said generating means with othernodes which correspond to said interface within self virtual node andadjusting it appropriately, and synchronizing it as unified internal IPaddress group information for self virtual node; and a means foradvertising self internal IP address group information which has beenunified by said synchronizing means to a node which corresponds to aninterface with an other virtual node.

[0094] In this case, it is possible to enhance the reliability of theinformation, since the node which corresponds to a plurality ofinterfaces advertises the same internal IP address group information tothe other virtual nodes.

[0095] Furthermore, said advertisement means may include: a means fordeciding whether or not an advertisement path is present from an othernode which corresponds to said interface within self virtual node to anode which corresponds to an interface with the same other virtual node;and a means for, when the decision result from said decision means is“yes”, performing advertisement via any advertisement path of self nodeor of said other node to the node which corresponds to said interface ofsaid other virtual node. In this case, it is possible to utilizeresources effectively without performing excessive advertisements.

[0096] It is possible to incorporate a means for receiving a packet forchecking reachability from an other node within self virtual node; ameans for summarizing the IP addresses of packets which have beenreceived by said receiving means and generating internal address groupinformation which is related to a node within self virtual node; and ameans for advertising the internal IP address group information whichhas been generated by said generating means to the node whichcorresponds to the interface with the other virtual node.

[0097] In this case, if the internal address IP group informationbetween different nodes which correspond to interfaces within the samevirtual node is different, it is possible to obtain information forpractical use in path computation by permitting this, since it ispossible to be aware from the advertisements that the reachability isdifferent, for nodes for which the interfaces to which they correspondare different even though they are in the same virtual node.

[0098] It is possible to incorporate a means for receiving from an othernode within self virtual node a packet for checking reachability whichincludes information to the effect that self node is the one with then-th cheapest link cost from the point of view of said other node; ameans for summarizing the IP addresses of packets which have beenreceived by said receiving means and generating internal IP addressgroup information which is related to a node within self virtual nodefor each of said n values; and a means for advertising the internal IPaddress group information which has been generated by said generatingmeans to the node which corresponds to the interface with the othervirtual node.

[0099] In this case, it is possible to classify the reachabilityinformation according to the class of the link cost, and it is possibleto obtain information which is rough but useful for the pathcomputation. Furthermore, since it is rough information, there is theadvantageous aspect that it is possible to reduce the amount of data.

[0100] Or, it is possible to incorporate a means for advertising to anode which corresponds to an interface on the same level as self nodelink information about a link on the same level as self node which hasbeen connected to self node and link cost information for said link, anda means for receiving, from a node which corresponds to an interface onthe same level with self node, advertisement of link information with anode which corresponds to said interface on the same level with selfnode, and link cost information for said link, and storing saidinformation.

[0101] In this case, advertisement is only performed between self nodeand a node which corresponds to an interface upon the same level, andfurthermore the information which is stored is only information betweenself node and the node which corresponds to an interface upon the samelevel. Due to this, it is possible to reduce the volume ofadvertisements and the amount of data which is to be stored by the nodewhich corresponds to the interface. However, it is not possible toperform a path computation which affects a higher level, since there isonly awareness of information between self node and a node whichcorresponds to an interface upon the same level.

[0102] It is desirable further to incorporate a means for, ahead of pathcomputation, requesting and obtaining, from said node which correspondsto said interface, link information with a node which corresponds to aninterface with the next highest level than self node, and link costinformation for said link.

[0103] With the node which has been explained above being incorporatedin a layered network, in the path search of nodes in this type oflayered network, for example, it is desirable for the source node forpath establishment to include: a means for specifying a virtual node towhich said destination node belongs from the IP address of thedestination node for path establishment, based upon the external IPaddress group information; and a means for searching for a path to thenode which corresponds to the interface of the virtual node to whichsaid destination node belongs which has been specified by saidspecifying means, based upon link information between a node whichcorresponds to an interface of self virtual node, and a node whichcorresponds to an interface of a virtual node on level 2 or higher, andlink cost information for said link.

[0104] In this case, finally, the source node is able to perform pathsearching up to the node which corresponds to the interface of thevirtual node to which the destination node belongs. In this case, as faras the path from the node which corresponds to said interface to thedestination node is concerned, it will be acceptable to entrust thismatter to said node which corresponds to said interface.

[0105] Or, it is possible to incorporate: a means for requesting andobtaining, from a node which corresponds to an interface of a virtualnode to which said destination node belongs, link information for withinsaid virtual node, and link cost information for said link; and a meansfor searching for, in addition to the path which has been searched outby said means for searching out a path to a node which corresponds to aninterface of a virtual node to which said destination node belongs, apath to said destination node from said node which corresponds to saidinterface, based upon link information which has been obtained by saidrequesting and obtaining means, and link cost information for said link.

[0106] In this case, it is possible to take the entire path as being thepath which the source node expects, since it is possible to performsearching for the path within the virtual node to which the destinationnode belongs on the side of the source node as well.

[0107] Or, it is possible to incorporate: a means for requesting andobtaining, from a node which corresponds to an interface of a virtualnode which is included in a path from self node to said destinationnode, link information for within said virtual node, and link costinformation for said link; and a means for searching out a path withinsaid virtual node which is included in the path from self node to saiddestination node, based upon said link information and said link costinformation for said link which have been obtained by said requestingand obtaining means.

[0108] In this case, it is possible for the source node to search forthe entire path from the source node to the destination node in detail,and it is possible for the establishment of the detailed path to beperformed by the source nodes.

[0109] Or, it is possible for the source node for path establishment toincorporate: a means for specifying a virtual node to which saiddestination node belongs from the IP address of the destination node forpath establishment, based upon the external IP address groupinformation; and a means for notifying to the destination node to whicha path is to be established information which specifies on which levelis the virtual node of the topmost level for which path computation fromself node to the node which corresponds to the interface is possiblebased upon information about a link between a node which corresponds toan interface of self virtual node and a node which corresponds to aninterface of a virtual node of level 2 or greater and link costinformation for said link, and the result of searching for a path fromself node to the node which corresponds to said interface for which thelink cost is the lowest in order up to the n-th lowest; and for saiddestination node to incorporate a means for, along with searching out apath from self node to the node which corresponds to the interface withthe virtual node of said topmost level for which path computation fromsaid source node to the node which corresponds to the interface ispossible based upon said information which has been notified, alsocombining said search results with the results of searching for a pathup to said n-th lowest one, and notifying the path for which the linkcost is the minimum to said source node as the final path which has beenfound.

[0110] In this case, the destination node acts more as the master in thepath computation than does the source node. For example, if it isnecessary to perform computation of paths from a single source node to alarge number of destination nodes, then, if said system with the sourcenode performing this large number of path computations all together isapplied to a case in which the processing burden upon the source nodehas become extremely heavy, it is possible to alleviate the processingburden by dispersing this processing burden among the large number ofdestination nodes.

[0111] It is desirable further to incorporate: a means for referring tolink information which has been stored in said storing means anddeciding whether or not a link which connects self virtual node and another virtual node is connected to self node; a means for when,according to the decision result of this decision means, a link whichconnects self virtual node and an other virtual node is connected toself node, deciding whether or not self node corresponds to atermination point for a layer of an LSP which has been established oversaid link; and a means for when, according to the decision result ofthis decision means, self node corresponds to said termination point,recognizing that self node is a node which corresponds to saidinterface, and exercising a function which corresponds to saidinterface.

[0112] The network which employs the present invention is a multi layernetwork. With a multi layer network, for example, LSPs of a plurality oflayers are mixed together, such as a Lambda path upon the Lambda layer,a TDM-LSP upon the TDM layer, and a packet path upon the IP layer.Furthermore, nodes which have various types of function are mixedtogether, such as nodes which have a wavelength switching function,nodes which have a packet switching function, and nodes which have bothof these functions. If the layered network of the present invention isapplied to this type of multi layer network, Lambda paths, TDM-LSPs, andpacket paths are also mixed together upon the LSPs which are connectedbetween the virtual nodes.

[0113] With a virtual node in the above described type of environment,if a node which has the function of terminating an LSP between virtualnodes has terminated said LSP upon the layer of said LSP, said node isestablished as the node which corresponds to the interface. Accordingly,if this LSP is a Lambda path, an optical cross connect device or thelike which is endowed with a wavelength switching function is taken asthe node which corresponds to the interface. Or, if this LSP is a packetpath, a router or the like which is endowed with a packet switchingfunction is taken as the node which corresponds to the interface.

[0114] It is desirable further to incorporate a means for observing theresource utilization state related to self node; a means for, if, basedupon the results of observation by this observation means, no room isavailable in the resources which are used for data transmission toanother node within self virtual node and self node corresponds to saidinterface, along with exercising a function as a node which belongs toan other virtual node of level 1 to which self node is connected, alsoupdating information about the virtual node to which self node belongsalong with change of said associated virtual node; a means foradvertising the change of contents of this updating means; and a meansfor, when a said advertisement has been received from an other node,updating the information about the virtual node to which self nodebelongs based upon said advertisement.

[0115] In other words, when generating a virtual node, it is inevitableto divide nodes for which from the beginning no link exists betweendifferent virtual nodes. With the present invention, in addition tothis, even if the availability of resources upon a link which existsbetween nodes has disappeared so that the reachability has failed, itbecomes an object of being divided up into virtual nodes. In this case,it is possible to enhance the efficiency and the accuracy of pathcomputation and packet transmission, since it is possible to construct alayered network which reflects the presence or absence of reachabilityin real time.

[0116] It is desirable further to incorporate a means for observing thecost of a link which is related to self node; a means for, if, basedupon the results of observation by this observation means, the link costwhich is used for data transmission to an other node within self virtualnode is greater than a threshold value, and self node corresponds tosaid interface, along with activating a function as a node which belongsto an other virtual node of level 1 to which self node is connected,updating the information about the virtual node to which self nodebelongs along with change of said associated virtual node; a means foradvertising the updated contents which have been updated by thisupdating means; and a means for, when a said advertisement has beenreceived from an other node, updating the information about the virtualnode to which self node belongs based upon said advertisement.

[0117] In other words, when creating the virtual node, it is inevitablethat nodes between which no link exists from the beginning will bedivided up into different virtual nodes. With the present invention, inaddition to this, even if a link exists between certain nodes, if thelink cost of said link has exceeded the threshold value, it becomes anobject of being divided up into virtual nodes. In this case, since it ispossible to keep the link cost of passing via the virtual nodes below afixed value, for example, it is possible to implement a layered networkin which it is not necessary to advertise link cost information which isalready known.

[0118] A sixth aspect of the present invention is a layered networkwhich includes a node according to the present invention.

[0119] [Method for Building a Layered Network]

[0120] A ninth aspect of the present invention is a method for buildinga layered network, wherein when, corresponding to a layer of an LSPwhich has been established in a link between self virtual node andanother virtual node, a node which is endowed with a function ofterminating an LSP of said layer has terminated an LSP of said layer,said node is established as a node which corresponds to said interface.

[0121] Or, in the method for building a layered network according to thepresent invention, it is possible, when there is no capacity inresources which are used for data transmission over links which havebeen established between nodes, to separate said nodes into differentvirtual nodes.

[0122] Or, in the method for building a layered network according to thepresent invention, it is possible, when the link cost for datatransmission over links which have been established between nodes hasexceeded a threshold value, to separate said nodes into differentvirtual nodes.

[0123] [Network Control Device]

[0124] A tenth aspect of the present invention is a network controldevice which controls the nodes which make up a layered network of thepresent invention all together, comprising a means for, when,corresponding to a layer of an LSP which has been established in a linkbetween self virtual node and another virtual node, a node which isendowed with a function of terminating an LSP of said layer hasterminated an LSP of said layer, establishing said node as a node whichcorresponds to said interface.

[0125] Or, it is desirable for the network control device of the presentinvention to incorporate a means for, when there is no vacant capacityin resources which are used for data transmission over links which havebeen established between nodes, dividing up said nodes into differentvirtual nodes.

[0126] Or, it is desirable for the network control device of the presentinvention to incorporate a means for, when the link cost for datatransmission over links which have been established between nodes hasexceeded a threshold value, dividing up said nodes into differentvirtual nodes.

[0127] As has been explained above, according to the present invention,it is possible to implement enlargement of the scale of a large scalenetwork, even if it is a network for which complicated processing isrequired, such as a multi layered network; and, furthermore, since it ispossible to perform path computation after having specified the rangeover which the path computation is required, it is possible to eliminatecomputation which has become unnecessary, and accordingly it is possibleto perform the path computation at high efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[0128]FIG. 1 is a schematic figure showing a multi layer network.

[0129]FIG. 2 is a figure showing the way in which a multi layerednetwork of a first preferred embodiment of the present invention isdivided up into cells, made into virtual nodes, and layered.

[0130]FIG. 3 is a figure showing the way in which the multi layernetwork of the first preferred embodiment is made into virtual nodes.

[0131]FIG. 4 is a schematic figure showing a node according to the firstpreferred embodiment of the present invention.

[0132]FIG. 5 is a functional block diagram showing a node according to asecond preferred embodiment of the present invention.

[0133]FIG. 6 is a functional block diagram showing a node according to athird preferred embodiment of the present invention.

[0134]FIG. 7 is a figure showing a method of allotting switchingcapability to an interface of a virtual node according to a fourthpreferred embodiment of the present invention.

[0135]FIG. 8 is a figure showing a method of allotting switchingcapability to an interface of a virtual node according to a fifthpreferred embodiment of the present invention.

[0136]FIG. 9 is a figure showing an outline of LSP establishment cost ina virtual network according to a sixth preferred embodiment of thepresent invention.

[0137]FIG. 10 is a figure showing a method of assigning a cost ofpassing through the virtual node according to a ninth preferredembodiment of the present invention.

[0138]FIG. 11 is a functional block diagram showing a layered networknode according to the ninth preferred embodiment of the presentinvention.

[0139]FIG. 12 is a figure showing a method of assigning a cost ofpassing through the virtual node according to a tenth preferredembodiment of the present invention.

[0140]FIG. 13 is a figure showing a method of assigning a cost of thevirtual node according to an eleventh preferred embodiment of thepresent invention.

[0141]FIG. 14 is a figure showing a method of assigning a cost of thevirtual node according to a twelfth preferred embodiment of the presentinvention.

[0142]FIG. 15 is a figure showing a method of assigning a cost ofpassing through the virtual node according to a thirteenth preferredembodiment of the present invention.

[0143]FIG. 16 is a figure showing a method of assigning a cost ofpassing through the virtual node according to a fourteenth preferredembodiment of the present invention.

[0144]FIG. 17 is a figure showing a path selection sequence of aseventeenth preferred embodiment of the present invention.

[0145]FIG. 18 is a functional block diagram showing a layered networknode according to the seventeenth preferred embodiment of the presentinvention.

[0146]FIG. 19 is a figure showing a path selection sequence of aneighteenth preferred embodiment of the present invention.

[0147]FIG. 20 is a figure showing a network management system of annineteenth preferred embodiment of the present invention.

[0148]FIG. 21 is a figure showing a network management system of atwentieth preferred embodiment of the present invention.

[0149]FIG. 22 is a figure showing a link bundling system of atwenty-first preferred embodiment of the present invention.

[0150]FIG. 23 is a figure showing a link bundling system of atwenty-second preferred embodiment of the present invention.

[0151]FIG. 24 is a figure showing the way in which a network is dividedup into cells, is made into virtual nodes, and is layered.

[0152]FIG. 25 is a figure showing the topology of a layered network.

[0153]FIG. 26 is a block structure diagram of a non border nodeaccording to a twenty-fourth preferred embodiment of the presentinvention.

[0154]FIG. 27 is a block structure diagram of a border node according tothis twenty-fourth preferred embodiment of the present invention.

[0155]FIG. 28 is a figure for explanation of a path search methodaccording to this twenty-fourth preferred embodiment of the presentinvention.

[0156]FIG. 29 is a block structure diagram of a non border nodeaccording to a twenty-fifth preferred embodiment of the presentinvention.

[0157]FIG. 30 is a block structure diagram of a border node according tothis twenty-fifth preferred embodiment of the present invention.

[0158]FIG. 31 is a block structure diagram of a non border nodeaccording to a twenty-sixth preferred embodiment of the presentinvention.

[0159]FIG. 32 is a block structure diagram of an essential portion of aborder node according to this twenty-sixth preferred embodiment of thepresent invention.

[0160]FIG. 33 is a block structure diagram of a non border nodeaccording to a twenty-seventh preferred embodiment of the presentinvention.

[0161]FIG. 34 is a block structure diagram of an essential portion of aborder node according to this twenty-seventh preferred embodiment of thepresent invention.

[0162]FIG. 35 is a block structure diagram of an essential portion of anon border node according to a twenty-eighth preferred embodiment of thepresent invention.

[0163]FIG. 36 is a block structure diagram of an essential portion of aborder node according to this twenty-eighth preferred embodiment of thepresent invention.

[0164]FIG. 37 is a figure showing the general concept of the operationof this twenty-eighth preferred embodiment of the present invention.

[0165]FIG. 38 is a figure showing the case when advertisement isperformed from a plurality of border nodes within self virtual node tothe same border node within an other virtual node.

[0166]FIG. 39 is a block structure diagram of an external advertisementsection of this twenty-eighth preferred embodiment of the presentinvention.

[0167]FIG. 40 is a block structure diagram of an essential portion of aborder node according to a twenty-ninth preferred embodiment of thepresent invention.

[0168]FIG. 41 is a block structure diagram of essential portions of anon border node according to thirtieth, thirty-first, and thirty-secondpreferred embodiments of the present invention.

[0169]FIG. 42 is a block structure diagram of an essential portion of aborder node according to the thirty-second preferred embodiment of thepresent invention.

[0170]FIG. 43 is a block structure diagram of an essential portion of anon border node according to a thirty-third preferred embodiment of thepresent invention.

[0171]FIG. 44 is a general conceptual view of the scope of level 1 of anon border node according to a thirty-third preferred embodiment of thepresent invention.

[0172]FIG. 45 is a block structure diagram of an essential portion of aborder node according to a thirty-fourth preferred embodiment of thepresent invention.

[0173]FIG. 46 is a general conceptual view of the scope of level 2 of aborder node according to this thirty-fourth preferred embodiment of thepresent invention.

[0174]FIG. 47 is a figure for explanation of a path search methodaccording to a thirty-fifth preferred embodiment.

[0175]FIG. 48 is a figure for explanation of a path search methodaccording to a thirty-sixth preferred embodiment of the presentinvention.

[0176]FIG. 49 is a block structure diagram of an essential portion of anon border node according to this thirty-sixth preferred embodiment ofthe present invention.

[0177]FIG. 50 is a sequence figure for explanation of another pathsearch method according to this thirty-sixth preferred embodiment of thepresent invention.

[0178]FIG. 51 is a figure for explanation of the definition of a bordernode.

[0179]FIG. 52 is a figure for explanation of the definition of a bordernode.

[0180]FIG. 53 is a block structure diagram of an essential portion of anode according to a thirty-seventh preferred embodiment of the presentinvention.

[0181]FIG. 54 is a figure for explanation of a separation method of avirtual node according to thirty-eighth, thirty-ninth, forty-second, andforty-third preferred embodiments of the present invention.

[0182]FIG. 55 is a block structure diagram of an essential portion of anode according to the thirty-eighth preferred embodiment of the presentinvention.

[0183]FIG. 56 is a block structure diagram of an essential portion of anode according to a thirty-ninth preferred embodiment of the presentinvention.

[0184]FIG. 57 is a block structure diagram of an essential portion of anode according to a fortieth preferred embodiment of the presentinvention.

[0185]FIG. 58 is a block structure diagram of an essential portion of anetwork control device of a forty-first preferred embodiment of thepresent invention.

[0186]FIG. 59 is a block structure diagram of an essential portion of anetwork control device of a forty-second preferred embodiment of thepresent invention.

[0187]FIG. 60 is a block structure diagram of an essential portion of anetwork control device of a forty-third preferred embodiment of thepresent invention.

[0188]FIG. 61 is a block structure diagram of an essential portion of anetwork control device of a forty-fourth preferred embodiment of thepresent invention.

[0189]FIG. 62 is a figure showing an example of a network which is madefrom a plurality of network layers.

DETAILED DESCRIPTION OF THE INVENTION

[0190] While preferred embodiments of the invention have been describedand illustrated above, it should be understood that these are exemplaryof the invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

THE FIRST PREFERRED EMBODIMENT

[0191] First, a network which includes layered network nodes will beexplained. FIG. 1 is a schematic view of such a network. This network ismade up from a plurality of network layers, and it will be assumed thatit comprises an IP layer, a TDM layer, and a Lambda layer. Each of thenodes in this network advertises its link state, which is made up frominformation such as IP address, maximum link band, usage band, and thelike.

[0192] Starting from this link state, a node which is to establish anLSP performs a computation for whether or not to establish a new TDM LSPor Lambda path for establishing an IP LSP, and, if such a TDM LSP orLambda path is to be newly established, also performs a computation fordetermining upon which path the cost for establishing the LSP will bethe least; and then it performs establishment of the LSP. Furthermore,when rearranging the path of some IP LSP, at the same time, computationsare also made as to whether change of the path of the Lambda path of thelayer below is necessary, and the like. With a network like the onedescribed above, it becomes impossible to maintain scalability upon anyfixed scale, since along with increase of the network scale, the volumeof link state advertisements, the amount of computation which isrequired for path computation, and the like progressively increase. Itis considered that the same thing will occur as the number of layershandled together increases.

[0193]FIG. 2 shows the situation when a multi layer network like the onedescribed above is layered by being separated into cells and by beingmade into virtual nodes. In this example, layering is performed down tothe third level (Level 3). Furthermore, in FIG. 3, the situation isshown in which the entire network has been made into a virtual node.

[0194] This type of network is implemented with the first preferredembodiment of the present invention. FIG. 4 is a schematic figureshowing a node for this purpose. This node collects together link stateinformation which gives the state of the present node and the states oflinks which are connected to the present node, and stores it in a linkstate database LSDB-L1. This link state information is advertised toother nodes via an advertisement section P. Furthermore, link stateinformation both from the present node and also from other nodes whichare included within the same virtual node is also advertised via theadvertisement section P. From among the information which has arrived byadvertisement at the advertisement section P, the Level 1 link stateinformation is picked out and is stored in the link state databaseLSDB-L1. If self node is disposed at a location where an interface witha virtual node is present (the nodes A, B, and C in FIG. 3), then selfnode comes to serve the function of a border node. Using an LSabstraction section LS1, a node which has been chosen as a border nodeabstracts the link state information of the link state database LSDB-L1to link state information for use at Level 2, and, along with storingthis in a link state database LSDB-L2, also advertises it via theadvertisement section P to the exterior of the virtual node as interfaceinformation for the virtual node.

[0195] In the same manner, an LS abstraction section LS2 repeats theoperation of obtaining link state information to be stored in a linkstate database LSDB-L3 from the link state information in the link statedatabase LSDB-L2, for its level of the network.

THE SECOND PREFERRED EMBODIMENT

[0196] With the second preferred embodiment of the present invention, asshown in FIG. 5, along with the link state information which is storedin the link state database LSDB-L1, a switching capability of theinterface of the virtual node of Level 2 is obtained by a switchingcapability allotment section (shown in the figure as a SC allotmentsection) SC of the LS abstraction station LS1. And there is provided afunction of, along with storing these results in the link state databaseLSDB-L2, also advertising them via the advertisement section P to theexterior of the virtual node.

[0197] In the same manner, the LS abstraction section LS2 repeats theoperation of obtaining link state information to be stored in the linkstate database LSDB-L3 from the link state information in the link statedatabase LSDB-L2, for its level of the network. FIG. 5 is a functionalblock diagram of the node at this time.

THE THIRD PREFERRED EMBODIMENT

[0198] With the third preferred embodiment of the present invention, asshown in FIG. 6, along with the link state information which is storedin the link state database LSDB-L1, a switching capability of theinterface of the virtual node of Level 2 is obtained by a switchingcapability allotment section SC of the LS abstraction station LS1, andalso the cost associated with going via self virtual node is computed bya cost computation section C. And there is provided a function of, alongwith storing these results in the link state database LSDB-L2, alsoadvertising them via the advertisement section P to the exterior of thevirtual node.

[0199] In the same manner, the LS abstraction section LS2 repeats theoperation of obtaining link state information to be stored in the linkstate database LSDB-L3 from the link state information in the link statedatabase LSDB-L2, for its level of the network. FIG. 6 is a functionalblock diagram of the node at this time.

THE FOURTH PREFERRED EMBODIMENT

[0200] With the fourth preferred embodiment of the present invention,the switching capability which is allocated in the second and the thirdpreferred embodiments is regulated. FIG. 7 shows the method of allottingswitching capability to the interfaces of a virtual node. Here, layersof the LSP which can be established between the interfaces via theinterior of the virtual node are allotted to the interface as switchingcapability. Accordingly, switching capability is allocated dependentupon the output ports, as well as upon the input ports.

[0201] Accordingly, as for the switching capability of the interfaces ofthe virtual node of FIG. 7, while for the interfaces a1, a2, and c2 itis PSC (Packet Switching Capability)+LSC (Lambda Switching Capability),by contrast, for the interfaces b and c1 it becomes PSC. By performingallotment of switching capability planned as far as the output ports ofthe LSP in this manner, it becomes possible accurately to advertise tothe exterior of the cell which interfaces can be used to establish LSPsof which layers.

THE FIFTH PREFERRED EMBODIMENT

[0202] With the fifth preferred embodiment of the present invention, theswitching capability which is allocated in the second and the thirdpreferred embodiments is regulated. FIG. 8 shows a method of allottingswitching capability to the interfaces of a virtual node. Here a systemis implemented of allotting the switching capabilities of the borderrouters within the cells at the interfaces of the virtual node asswitching capability of the interfaces of the virtual node.

[0203] In FIG. 8, the interfaces al and a2 have an LSC switchingcapability, the interfaces b and c1 have a PSC switching capability, andthe interface c2 has both an LSC+a PSC switching capability. In thismanner, it is possible to reduce the volume of advertisements ofswitching capability of the virtual routers.

THE SIXTH PREFERRED EMBODIMENT

[0204] When establishing an LSP over a network, it has been contemplatedto vary the switching capabilities which are possessed by the interfacesof the virtual nodes while utilizing the network resources. In the caseof this sixth preferred embodiment of the present invention, by takingas a trigger the fact that the switching capability which is possessedby the interfaces of the virtual nodes which have been shown above inrelation to the first through the fifth preferred embodiments haschanged, and by advertising this fact to the other virtual nodes, itbecomes possible for the path selection when establishing an LSPaccurately to reflect the actual state of the network.

THE SEVENTH PREFERRED EMBODIMENT

[0205] When establishing an LSP over a network, it has been contemplatedto vary the switching capabilities which are possessed by the interfacesof the virtual nodes while utilizing the network resources. In the caseof this seventh preferred embodiment of the present invention, byperiodically advertising to the other virtual nodes changes of theswitching capability which is possessed by the interfaces of the virtualnodes which have been shown above in relation to the first through thefifth preferred embodiments, it becomes possible to alleviate the burdenof the advertisements, while ensuring that the path selection whenestablishing an LSP accurately reflects the actual state of the network.

THE EIGHTH PREFERRED EMBODIMENT

[0206]FIG. 9 shows an outline of the LSP establishment cost in a virtualnode network, in an eighth preferred embodiment of the presentinvention. The LSP establishment cost in a virtual node network is thecost of the links and the cost of going through the virtual nodes. Inother words:

Cost of establishing an LSP over a virtual network=Sum of link costs+Sumof costs of passing via the virtual nodes.

[0207] In this case, the layers of the LSPs which the virtual node canhandle are shown by switching capability. Switching capabilityattributes are assigned to the interfaces of the virtual nodes. In thiscase, a cost of going through a virtual node is assigned for eachswitching capability which is possessed by the interfaces of the virtualnode. This is because sometimes the cost is different, when goingthrough the virtual node, between the case of going via an LSP on the IPlayer and the case of going via an LSP on the Lambda layer. It ispossible to determine upon which layer it is best to establish an LSP byperforming comparison of the cost values for each of these layers.

THE NINTH PREFERRED EMBODIMENT

[0208]FIG. 10 shows a method of assigning the cost of going via avirtual node, in a ninth preferred embodiment of the present invention.The interior of the virtual node is constituted by a network, and thelinks which connect it to the exterior of the cell are taken asinterfaces. In this case, the layers for which an LSP can be establishedbetween an input interface and an output interface of the virtual nodeare different for different ones of the interfaces. An example of thisis shown in FIG. 10, displayed as a matrix set up between the input andoutput interfaces. Here, if the input and output interfaces aredifferent, the path within the cell is also different, so that thecorresponding cost incurred is also different. Accordingly, it isassumed that costs are allocated to the individual switchingcapabilities in the matrix between the input and output interfaces ofthe virtual node.

[0209] In this case, the cost which is allotted to the individualswitching capability in the matrix between the input and outputinterfaces of the virtual node is the cost of the path for which it ispossible to establish an LSP at the minimum cost, as selected by a costselection section from among the path candidates for which an LSP on thesaid switching capability layer can be established between these inputand output interfaces. FIG. 11 shows the functional blocks of thelayered network node at this time. The functional blocks of FIG. 11 areset up by further adding a cost selection section C to the functionalblocks of FIG. 6, and, herein, switching capability is allotted by aswitching capability allotment section SC, computation and allotment ofcosts is added by the cost computation section C, and selection of thepath over which an LSP can be established at the minimum cost isperformed by a cost selection section S. The cost of establishing an LSPwhich has been set up in this manner is allotted as a cost of theinterface of the virtual node.

[0210] As has been explained above, this is linked to reduction of thevolume of advertisements, since advertisement is performed toexternally, not for the candidates of all costs via the virtual node,but only for those of the minimum cost.

THE TENTH PREFERRED EMBODIMENT

[0211]FIG. 12 shows a method of assigning the cost via a virtual node,in a tenth preferred embodiment of the present invention. The interiorof the virtual node is constituted by a network, and the links whichconnect it to the exterior of the cell are taken as interfaces. In thiscase, the layers for which an LSP can be established between an inputinterface and an output interface of the virtual node are different fordifferent ones of the interfaces. An example of this is shown in FIG.10, displayed as a matrix set up between the input and outputinterfaces. Here, if the input and output interfaces are different, thepath within the cell is also different, so that the corresponding costincurred is also different. Accordingly, costs are individuallyallocated to the switching capabilities in the matrix between the inputand output interfaces of the virtual node.

[0212] In this case, the cost which is allotted to the individualswitching capability in the matrix between the input and outputinterfaces of the virtual node is the cost of establishing the LSP whosepath has the minimum number of hops upon the said layer which can beestablished between the said combination of input interface and outputinterface, and, if a plurality of such paths of the minimum number ofhops exist, is the minimum cost from among the candidates.

[0213] Although, in this manner, a system is used which, after in afirst stage performing limitation to the paths for which an LSP can beestablished in the minimum number of hops, selects one from among thelimited candidates in a second stage, it is possible to omit the searchwhich is performed in the first stage after having performed it justonce, since, provided that no change occurs in the network topology, theresults of this first stage search for a path in the minimum number ofhops in the first stage do not change.

[0214] According to this method, it becomes possible to determine thecosts which are allocated to the interfaces of the virtual node moreeasily.

THE ELEVENTH PREFERRED EMBODIMENT

[0215]FIG. 13 shows a method of assigning costs to a node in an eleventhpreferred embodiment of the present invention. The cost of a path isobtained by adding a node cost to a link cost. The cost of going throughthe node is determined by the number of interfaces which are possessedby that node. The cost of passing through the node upon any layer istaken as the reciprocal of the number, among the interfaces which areendowed with the switching capability of that layer, of the ones whichare currently unused.

THE TWELFTH PREFERRED EMBODIMENT

[0216]FIG. 14 shows a method of assigning costs to a node in a twelfthpreferred embodiment of the present invention. The cost of a path isobtained by adding a node cost to a link cost. The cost of going throughthe node is determined by the number of interfaces which are possessedby that node. The cost of passing through the node upon any layer istaken as being the number, among the interfaces which are endowed withthe switching capability of that layer, of the ones which are currentlybeing used, divided by the total number thereof.

THE THIRTEENTH PREFERRED EMBODIMENT

[0217]FIG. 15 shows a method of assigning a cost to passing through avirtual node in a thirteenth preferred embodiment of the presentinvention. A cost of passing through the virtual node is not allocatedto each interface which is possessed by the virtual node; rather, it isallocated as a single cost for them all. The method of performing thisallotment is to take this single cost as being the reciprocal of thetotal number of unused ones among the interfaces which are endowed withthe switching capability of this layer and which the nodes which areincluded in self virtual node are endowed with.

THE FOURTEENTH PREFERRED EMBODIMENT

[0218]FIG. 16 shows a method of assigning a cost to passing through avirtual node. Again, a cost of passing through the virtual node is notallocated to each interface which is possessed by the virtual node;rather, it is allocated as a single cost for them all. The method ofperforming this allotment is to take this single cost as being thenumber, among the interfaces which are endowed with the switchingcapability of that layer and which the nodes which are included in selfvirtual node are endowed with, of the ones which are currently beingused, divided by the total number thereof.

THE FIFTEENTH PREFERRED EMBODIMENT

[0219] In this fifteenth preferred embodiment of the present invention,since the cost of passing through a virtual node varies according to theopen or closed states of the interfaces for each switching capabilitywhich exists in its interior, accordingly the nodes which correspond tothe interfaces of the virtual node periodically perform recomputation ofthe cost.

THE SIXTEENTH PREFERRED EMBODIMENT

[0220] In this sixteenth preferred embodiment of the present invention,since the cost of passing through a virtual node varies according to theopen or closed states of the interfaces for each switching capabilitywhich exists in its interior, accordingly the nodes which correspond tothe interfaces of the virtual node and which have received communicationthat a change has occurred immediately perform recomputation of thecost.

THE SEVENTEENTH PREFERRED EMBODIMENT

[0221]FIG. 17 shows a path selection sequence of a seventeenth preferredembodiment of the present invention. First, the network range forperforming path selection is determined. If, among the cells on thelowest level, destination nodes are present among the cells to which thesource nodes belong, the path selection is performed from among thesecells. If no destination node is present among these cells, the cellswhich include a source node are picked out from the cells of the nexthigher level, and an investigation is performed as to whether or not adestination node is present among these cells. If a destination node ispresent among these cells, then path selection is performed from amongthese cells; but if no destination node is present among these cells,then, in the same manner as before, an investigation is performed withthe cells on the next higher level. This series of investigations isrepeated until a destination node comes to light.

[0222] In the network range over which the path selection which has beendetermined upon is performed in this manner, the path selection of thevirtual node network is performed by the path selection section of thesaid level. Here, for a virtual node which has been chosen as a relaynode, the path selection of the virtual node network is performed withinthis cell by the path selection section of the said level in the samemanner. It becomes possible to determine upon a path from the sourcenode to the destination node by repeating this path selection until thelowest level. FIG. 18 shows the functional blocks of the layered networknode in this case. The functional blocks of FIG. 18 result from theaddition of an L1 path selection section RS1, an L2 path selectionsection RS2, and an L3 path selection section RS3 to the functionalblocks which were shown in FIG. 11.

[0223] In this manner, by adopting a method of progressively enlargingthe range for investigation in order from the lowest level until adestination node is brought to light, it becomes possible to discover adestination node very quickly in a network in which many LSPs areestablished between close nodes.

THE EIGHTEENTH PREFERRED EMBODIMENT

[0224]FIG. 19 shows the sequence of the eighteenth preferred embodimentof the present invention.

[0225] First, the network range for performing path selection isdetermined.

[0226] A check is made to determine whether or not, among the cells atthe topmost level, there exists a cell which includes both a source nodeand a destination node. If one such cell exists, then, in the samemanner, a check is made to determine whether or not, for the networkwithin this cell, there exists a cell which includes both a source nodeand a destination node, and this series of checks is repeated until thesource node and the destination node come to be included withindifferent cells. When it has been checked that the source node and thedestination node are included within different cells, the network whichincludes these cells is set as the range for performing path selection.

[0227] In the network range for performing path selection which has beendetermined upon in the above manner, path selection of the virtual nodenetwork is performed by the path selection section of the said level.Here, with a virtual node which has been chosen as a relay node, pathselection of the virtual node network is performed by the path selectionsection of the said level in the same manner as within this cell. Itbecomes possible to determine upon the path from the source node to thedestination node by repeating this path selection down to the lowestlevel. The functional blocks of the layered network node at this timeare shown in FIG. 18.

[0228] By employing this method in which the network range forperforming path selection is taken in order from the topmost level inthis manner for a network in which many LSPs are established betweendistant nodes, it becomes possible to discover the destination nodequickly.

THE NINETEENTH PREFERRED EMBODIMENT

[0229]FIG. 20 shows a network management system according to anineteenth preferred embodiment of the present invention.

[0230] When performing path selection as is done in the seventeenth andthe eighteenth preferred embodiments, in the state in which only theinput-output interfaces of the virtual node have been determined upon,it then becomes necessary to perform path selection for the networkwithin self virtual node.

[0231] In this case, a method has been conceived of undertaking the pathselection computation for the internal network by a node, or by avirtual node, which corresponds to the input-output interfaces of thevirtual node which are already decided upon.

THE TWENTIETH PREFERRED EMBODIMENT

[0232]FIG. 21 shows a network management system according to a twentiethpreferred embodiment of the present invention. When performing pathselection as is done in the seventeenth and the eighteenth preferredembodiments, in the state in which only the input-output interfaces ofthe virtual node have been determined upon, it then becomes necessary toperform path selection for the network within self virtual node.

[0233] In this case, it is possible to conceive of the path selectioncomputation for the internal network being undertaken by a node, or by avirtual node, which has been chosen from within the virtual node. By theadoption of this procedure, it becomes possible to prevent the pathselection computation procedure from being concentrated only upon theborder nodes.

THE TWENTY-FIRST PREFERRED EMBODIMENT

[0234]FIG. 22 shows a link bundling system according to a twenty-firstpreferred embodiment of the present invention. The network is divided upinto a plurality of cells, and, when these are defined as virtual nodes,the virtual nodes come to be connected together by the same number oflinks as the number of links by which the nodes themselves are connectedwithin the cells. When the virtualization of this network is performedby a hierarchical structure, a large number of links come to connectbetween these virtual nodes. In this case, when advertisement of thelink states between the virtual nodes is considered, increase of thenumber of links is believed to entail increase of the number of linkstate advertisements.

[0235] Due to this, if a plurality of links are present between thebases of the virtual nodes, it becomes possible to prevent increase ofthe number of link states by bundling together this plurality of linksand considering them all together as a single virtual link. In thiscase, the cost which is allotted to the interfaces is considered as amethod of advertising the interfaces which are connected together byself virtual link.

THE TWENTY-SECOND PREFERRED EMBODIMENT

[0236]FIG. 23 shows a link bundling system according to a twenty-secondpreferred embodiment of the present invention. The network is divided upinto a plurality of cells, and, when these are defined as virtual nodes,the virtual nodes come to be connected together by the same number oflinks as the number of links by which the nodes themselves are connectedwithin the cells. When the virtualization of this network is performedby a hierarchical structure, a large number of links come to connectbetween these virtual nodes. In this case, when advertisement of thelink states between the virtual nodes is considered, increase of thenumber of links is believed to entail increase of the number of linkstate advertisements.

[0237] Due to this, if a plurality of links are present between thebases of the virtual nodes, it becomes possible to prevent increase ofthe number of link states by bundling together this plurality of linksand considering them all together as a single virtual link. At thistime, the method is considered of bundling together the links which areendowed with the same switching capability. The cost of advertisement atthis time is considered to be the minimum one among the advertisementcosts which are possessed by the interfaces of the links which have beenbundled together. According to this method, along with reducing thenumber of the links, it becomes possible to advertise the minimum costwhen taking this path, for each switching capability. Therefore trafficengineering at higher accuracy becomes possible.

THE TWENTY-THIRD PREFERRED EMBODIMENT

[0238] It is possible to implement the layered network node, network,and layered path selection method of this preferred embodiment byutilizing a computer device, which is an information processing device.In other words, this twenty-third preferred embodiment of the presentinvention is a program which is distinguished in that, by beinginstalled upon a computer device, it causes that computer device toexecute procedures of, when establishing a LSP on any layer of thenetwork which includes the layered network node of this preferredembodiment of the present invention, when selecting a path from a sourcenode to a destination node: making a decision, by referring to said linkstate database of the lowest level 1, as to whether or not, among thesaid virtual nodes of level 1, the destination node is present withinthe same virtual node which includes the source node; and, if thedestination node is not present within any same virtual node as thesource node, making a decision, by referring to said link state databaseof the next higher level 2, as to whether or not the destination node ispresent in any of the virtual nodes of level 2 which include the saidsource node; and, by repeating this decision until the source node andthe destination node are included within the same virtual node,selecting the virtual node of a Nth level (where N is a natural number)which includes both the source node and the destination node; and, whenselecting a path of level N from the source node to the destination nodewithin self virtual node of level N which has been selected: performingpath selection of the virtual node group which is included in saidvirtual node of level N which has been selected with said selectionmeans of said level N based upon said link state database of said levelN; furthermore, when selecting a path of the next lower level (N-1) fromthe source node to the destination node among the virtual nodes whichare included in this path of level N which has been selected, performingpath selection with said selection means of said level (N-1) based uponsaid link state database of the next lowest level (N-1) than saidvirtual node which has been selected; and, by repeating this until thelowest level 1, selecting a path from the source node to the destinationnode.

[0239] Or, this twenty-third preferred embodiment of the presentinvention is a program which is distinguished in that, by beinginstalled upon a computer device, it causes that computer device toexecute procedures of, when establishing a LSP on any layer of thenetwork which includes the layered network node of this preferredembodiment of the present invention, when selecting a path from a sourcenode to a destination node: making a decision, for a network whichincorporates virtual nodes of a topmost level N, by referring to saidlink state database of said level N, as to whether or not thedestination node is present within the same virtual node which includesthe source node; and, if the destination node is indeed present withinthe same virtual node as the source node, making a decision, byreferring to said link state database of the next lower level (N-1) thanself virtual node, as to whether or not the source node and thedestination node are present in the same virtual node in the network ofthe next lower level (N-1) within self virtual node; and, by repeatingthis decision until the source node and the destination node areincluded within different virtual nodes, and selecting the virtual nodeof the next upward level (N-k) (where k is a natural number), selectingthe virtual node of the level (N-k) which includes both the source nodeand the destination node; and, when selecting a path of level (N-k) fromthe source node to the destination node within self virtual node:performing path selection of the virtual node group which is included insaid virtual node of level (N-k) which has been selected based upon saidlink state database of said level (N-k); furthermore, when selecting apath of the next lower level (N-k-1) from the source node to thedestination node with said selection means of said level (N-k) among thevirtual nodes which are included in this path of level (N-k) which hasbeen selected, performing path selection with said selection means ofsaid level (N-k-1) based upon said link state database of the nextlowest level (N-k-1) than said virtual node which has been selected;and, by repeating this until the lowest level 1, selecting a path fromthe source node to the destination node.

[0240] By recording the program of this preferred embodiment upon arecording medium of this preferred embodiment, it is possible to installthe program of this preferred embodiment upon a computer device by usingthis recording medium. Or it is possible to install the program of thispreferred embodiment directly upon a computer device via a network froma server upon which the program of this preferred embodiment is stored.

[0241] In this case, it is possible to implement extension to a largescale network by utilizing a computer device, and, furthermore, since itis possible to perform the computation after having specified a range oflayers upon which it is considered to be necessary to perform pathcomputation, it is possible to eliminate computation which would becomeinefficient, and it is possible to implement a layered network node,network, and layered path selection method which can perform pathcomputation at good efficiency.

[0242] The layered network of this preferred embodiment of the presentinvention will now be explained with reference to FIGS. 24 and 25. FIG.24 is a figure showing how the network is divided up into cells, is madeinto virtual nodes, and is layered. And FIG. 25 is a figure showing thetopology of the layered network.

[0243] As shown in Level 1 of FIG. 24, the layered network of thispreferred embodiment of the present invention is a layered network inwhich the nodes which make up the network are divided up into cells (theportions surrounded by the broken lines) which consist of one or aplurality of nodes, and these cells are defined as virtual nodes oflevel 1, so that these virtual nodes of level 1 constitute the virtualnetwork of level 1; and, as shown in Level 2 of FIG. 24, the saidvirtual nodes of level 1 which constitute the virtual network of level 1are furthermore divided into cells which are made up from one or aplurality of said virtual nodes and constitute virtual nodes of level 2,so that the layered network such as that shown in FIG. 24 is constitutedby building up a 1 to N level virtual network by repeating this type ofoperation of dividing into cells and making into virtual nodes once or aplurality N of times, and if, in the said layered network, a link existswhich connects between different virtual nodes of the same level or ofdifferent levels, then, when the node which corresponds to the point ofcontact between the interior of the virtual node upon this link and theexterior is defined as an interface, and the virtual node to which saidinterface is related on the highest level is at the level M(≦N), saidinterface is defined as serving as a plurality of layered interfacesfrom level 1 to M. In the example shown in FIG. 24, the layeringcontinues down to Level 3.

[0244] To classify the nodes which make up the layered network of thispreferred embodiment of the present invention on the large scale, theymay be divided up into nodes which correspond to said interfaces, andnodes which do not correspond to said interfaces. Herein, in thisdescription of the preferred embodiment of the present invention, thenodes which correspond to said interfaces will be termed border nodes,while the nodes which do not correspond to said interfaces will betermed non border nodes. Although In practice the border nodes are alsocapable of fulfilling the functions of the non border nodes, thefollowing explanation of the border nodes will be made with emphasisupon their functions which are different from those of the non bordernodes, in order to make the explanation easier to understand.

[0245]FIG. 25 shows a topology of this type of layered network. Thewhite circles in FIG. 25 are non border nodes upon level 1. The hatchedcircles in FIG. 25 are border nodes of level 1, and these correspond tointerfaces. Although these interfaces are border nodes of level 1, theyalso belong to level 2. The solid black circles in FIG. 25 are bordernodes of level 1, and these also correspond to interfaces. Althoughthese interfaces are border nodes of level 1, they also belong to level2 and to level 3. The circles shown by thin solid lines in FIG. 25 arevirtual nodes of level 2, while the circles shown by thick solid linesare virtual nodes of level. 3. The straight fine solid lines are linksof level 1, while the straight fine broken lines are links of level 2.Furthermore, the thick broken lines are links of level 3.

THE TWENTY-FOURTH PREFERRED EMBODIMENT

[0246] The twenty-fourth preferred embodiment of the present inventionis a preferred embodiment which is related to a non border node (shownas a white circle). The structure of such a non border node is shown inFIG. 26. This non border node according to the twenty-fourth preferredembodiment of the present invention is characterized by comprising: anadvertisement section 1 which advertises information about the linkswhich are connected to self node and link cost information about saidlinks to the other nodes within self virtual node; a retention sectionfor information within self virtual node which receives advertisementsof link information about links within self virtual node and link costinformation about said links from other nodes within self virtual node,and stores said information; and a retention section 3 for informationwithin other virtual nodes, which receives advertisements of linkinformation about links between the border nodes which correspond tointerfaces of self virtual node and the border nodes which correspond tointerfaces of a virtual node on a higher level than self virtual node,and link cost information about said links, from the border nodes whichcorrespond to the interfaces, and stores said information.

[0247] Since this border node is a node which has both the function ofan interface and also the same function as a non border node, itperforms advertisements just like said two elements together.

[0248] Furthermore, this non border node comprises an IP addressnotification section 4 which transmits its own IP address to a bordernode which corresponds to an interface of self virtual node, and theretention section 3 for information within other virtual nodes 3 storesexternal IP address group information, which is information about the IPaddresses of other nodes which belong to virtual nodes other than selfvirtual node and information about the virtual nodes to which said IPaddresses belong, which has been transmitted from the border nodes whichcorrespond to said interfaces.

[0249] Next, a border node according to this twenty-fourth preferredembodiment of the present invention will be explained with reference toFIG. 27. FIG. 27 is a block structure diagram of this border nodeaccording to the twenty-fourth preferred embodiment of the presentinvention. The border node according to the twenty-fourth preferredembodiment of the present invention comprises: an internal advertisementsection 21 which advertises information about links within self virtualnode to which self node has been connected and link cost informationabout the cost of said links, and information about links with a bordernode which corresponds to an interface with an other border node whichhas been connected to self node and link cost information about the costof said links, to other nodes within self virtual node; a retentionsection 2 for information within self virtual node which receivesinformation about links within self virtual node and link informationabout the cost of said links from other nodes within self virtual node,and stores said information; and a retention section 12 for informationwithin other virtual nodes which receives information about links onhigher levels and link information about the cost of said links from aborder node which corresponds to said interface with an other virtualnode, and stores said information.

[0250] Furthermore, it comprises: an IP address information collectionsection 14 which gathers together and stores IP address information fromother nodes within self virtual node, an external advertisement section15 which advertises to an other node which corresponds with an interfacewith an other virtual node IP address information which has beengathered together by this IP address information collection section 14,and a retention section 16 for IP address groups within other virtualnodes which stores the IP addresses of other nodes which belong tovirtual nodes other than self virtual node and external IP address groupinformation, which is information about the virtual nodes to which saidIP addresses belong, which has been advertised from border nodes whichcorrespond to interfaces with other virtual nodes, and transmits it toother nodes within self virtual node.

[0251] Next, the path searching method according to the twenty-fourthpreferred embodiment of the present invention which utilizes theinformation which self node has stored will be explained with referenceto FIG. 28. FIG. 28 is a figure for explaining this path searchingmethod according to the twenty-fourth preferred embodiment. The sourcenode for path establishment shown in FIG. 28, as shown in FIG. 26,comprises: a destination node position search section 5 which specifies,from the IP address of the destination node for path establishment, avirtual node to which said destination node belongs, based upon theexternal IP address group information; and a path search section 6 whichsearches out a path to a border node which corresponds with theinterface to the virtual node to which said destination node which hasbeen specified by the destination node position search section 5belongs, based upon information about links between the border nodewhich corresponds to the interface of self virtual node and the bordernode which corresponds with the interface of the virtual node of ahigher level than self virtual node, and link cost information aboutsaid links.

[0252] In other words, the destination node position search section 5searches out the virtual node to which the destination node belongs,based upon the external IP address group information which has beenstored in the retention section 3 for information within other virtualnodes. And the path search section 6 searches out a path to the bordernode with said virtual node, based upon the link information and thelink cost information which has been stored in the retention section 3for information within other virtual nodes.

[0253] With this path searching method according to the twenty-fourthpreferred embodiment of the present invention, although the source nodedoes not perform a search as far as a detailed path within the virtualnode to which the destination node belongs, provided that it does searchout a path to the border node of the virtual node to which thedestination node belongs, no evil effect will occur and cause a problemin practice, even if path searching to the destination node from saidborder node is delegated to said border node.

THE TWENTY-FIFTH PREFERRED EMBODIMENT

[0254] A non border node according to a twenty-fifth preferredembodiment of the present invention will now be explained with referenceto FIG. 29. FIG. 29 is a block structure diagram of this non border nodeaccording to the twenty-fifth preferred embodiment. This non border nodeaccording to the twenty-fifth preferred embodiment of the presentinvention is basically the same in structure as the non border node ofthe twenty-fourth preferred embodiment of the present invention shown inFIG. 26. The features by which it differs are that an external IPaddress group information capture section 7 is additionally provided,and that the retention section 3 for information within other virtualnodes does not store the external IP address group information.

[0255] The external IP address group information capture section 7requests and obtains the IP addresses of other nodes which belong tovirtual nodes other than self virtual node, and external IP addressgroup information, which is information about the virtual nodes to whichsaid IP addresses belong, from border nodes which correspond to saidinterface.

[0256] Next, a border node according to this twenty-fifth preferredembodiment of the present invention will be explained with reference toFIG. 30. FIG. 30 is a block structure diagram of an essential portion ofthis border node according to the twenty-fifth preferred embodiment. AnIP address group information retention section 17 within an othervirtual node of this border node according to the twenty-fifth preferredembodiment of the present invention stores the IP addresses of othernodes which belong to virtual nodes other than self virtual node, andexternal IP address group information, which is information about thevirtual nodes to which said IP addresses belong, which has beenadvertised from a border node which corresponds to an interface with another virtual node, and offers this external IP address groupinformation which has been stored to said other nodes, according torequests from said other nodes. Apart from this, it is the same as theborder node of the twenty-fourth preferred embodiment of the presentinvention as shown in FIG. 27. It should be understood that external IPaddress group information is not required in the advertisement contentsof the internal advertisement section 11, in this twenty-fifth preferredembodiment of the present invention.

[0257] This twenty-fifth preferred embodiment of the present inventionis applied in the case of using a network environment in which thedestination node shifts frequently. In other words although, with thistwenty-fifth preferred embodiment of the present invention, a necessityarises for the border node to perform transmission of update informationto the source node each time the destination node shifts, since, withthis twenty-fifth preferred embodiment, an offer of information isrequested from the source node to the border node only when the sourcenode performs path searching, the border node does not need to performtransmission of update information to the source node each time thedestination node shifts, so that it is possible to reduce the amount ofprocessing which is required, by comparison with the twenty-fourthpreferred embodiment of the present invention described above.

THE TWENTY-SIXTH PREFERRED EMBODIMENT

[0258] A non border node according to a twenty-sixth preferredembodiment of the present invention will now be explained with referenceto FIG. 31. FIG. 31 is a block structure diagram of this non border nodeaccording to the twenty-sixth preferred embodiment. This non border nodeaccording to the twenty-sixth preferred embodiment of the presentinvention comprises: an IP address and link cost notification section 8which transmits the IP address of self node and link cost informationbetween self node and the border node which corresponds to the interfaceof self virtual node, and link cost information, to said border nodewhich corresponds to said interface;

[0259] and an external IP address group and link cost informationretention section 9 which stores the IP addresses of other nodes whichbelong to virtual nodes other than self virtual node and external IPaddress group information, which is information about the virtual nodesto which said IP addresses belong, which has been transmitted fromborder nodes which correspond to said interface, and link costinformation from the border node which corresponds to said interface tosaid other node, in correspondence with the IP addresses of said othernodes.

[0260] With this non border node according to the twenty-sixth preferredembodiment of the present invention, the link cost information istransmitted to the border node by the IP address and link costnotification section, along with the IP address of self node 8, as faras said border node.

[0261] The link information and the external IP address group and linkcost information for within other virtual nodes are transmitted from theborder node, and they are respectively stored in the retention section 3for information within other virtual nodes and in the external addressgroup and link cost information retention section 9.

[0262] The destination node position search section 5 searches out thevirtual node to 5 which the destination node belongs, based upon theexternal IP address group information which has been stored in theexternal address group and link cost information retention section 9.And the path search section 6 searches out a path to the border nodewith said virtual node, based upon the link cost information which isstored in the external address group and link cost information retentionsection 9.

[0263] Next, a border node according to this twenty-sixth preferredembodiment of the present invention will be explained with reference toFIG. 32. FIG. 32 is a block structure diagram of this border nodeaccording to the twenty-sixth preferred embodiment of the presentinvention. As shown in FIG. 32, the border node according to thetwenty-sixth preferred embodiment of the present invention comprises: anIP address and link cost information collection section 18 which gatherstogether and stores IP address information from other nodes within selfvirtual node and link cost information between said other node and selfnode; an external advertisement section 19 which advertises to a bordernode which corresponds to an interface with an other virtual node the IPaddress information and link cost information which have been gatheredtogether by this IP address and link cost information collection section18; and an external IP address group and link cost informationcollection section 20 and an internal advertisement section 21 whichstores external IP address group information, which is information aboutthe IP addresses of other nodes which belong to virtual nodes other thanself virtual node and information about the virtual nodes to which saidIP addresses belong, which has been advertised from the border nodeswhich correspond to said interface of the other virtual node, and linkcost information from the border node which corresponds with saidinterface with said other virtual node to said other node, incorrespondence with the IP addresses of said other nodes, and transmitsit to other nodes within self virtual node.

[0264] Although, with this twenty-sixth preferred embodiment of thepresent invention, the source node cannot perform its searching as faras a detailed path within the virtual node to which the destination nodebelongs, nevertheless the source node is able to search out the path upto the destination node for which the link cost is the least, providedthat it can search out a path as far as the border node of the virtualnode to which the destination node belongs, since the link cost fromsaid border node up to the destination node is known.

THE TWENTY-SEVENTH PREFERRED EMBODIMENT

[0265] A non border node according to a twenty-seventh preferredembodiment of the present invention will now be explained with referenceto FIG. 33. FIG. 33 is a block structure diagram of this non border nodeaccording to the twenty-seventh preferred embodiment. By contrast withthe twenty-sixth preferred embodiment of the present invention describedabove, this non border node according to the twenty-seventh preferredembodiment of the present invention does not store external IP addressgroup and link cost information, but differs in that, when performingpath computation, an external IP address group and link cost informationcapture section 10 requests and obtains that information from the bordernode.

[0266] Next, a border node according to this twenty-seventh preferredembodiment of the present invention will be explained with reference toFIG. 34. FIG. 34 is a block structure diagram of an essential portion ofthis border node according to the twenty-seventh preferred embodiment.By contrast with the twenty-sixth preferred embodiment of the presentinvention shown in FIG. 32, this border node according to thetwenty-seventh preferred embodiment of the present invention differs inthat an external IP address group and link cost information collectionsection 22, along with storing external IP address group information,which is information about the IP addresses of other nodes which belongto virtual nodes other than self virtual node and information about thevirtual nodes to which said IP addresses belong, which has beenadvertised from the border nodes which correspond to said interface ofthe other virtual node, and link cost information from the border nodewhich corresponds with said interface with said other virtual node tosaid other node, in correspondence with the IP addresses of said othernodes, also, upon a request from an other node, offers to said othernode said external IP address group information and link costinformation which has been stored.

[0267] Since, when the source node requests an offer of information froma border node, it is possible to obtain information about the virtualnode to which said destination belongs and the link cost informationfrom said border node up to said destination node by performingdesignation of the IP address of the destination node, it is possible toobtain the minimum amount of information which is required, andaccordingly it is possible to alleviate the amount of processing uponthe border node and upon the non border node which becomes the sourcenode.

[0268] In the same manner as in the twenty-fifth preferred embodiment ofthe present invention, this twenty-seventh preferred embodiment of thepresent invention is applied in the case of utilizing a networkenvironment in which the destination node changes frequently. In otherwords although, with the twenty-sixth preferred embodiment of thepresent invention, the necessity arises for the border node to performtransmission of information which has been updated to the source nodeeach time the destination node shifts, by contrast, in thistwenty-seventh preferred embodiment of the present invention, since anoffer of information is only requested from the source node to theborder node when the source node perform path searching, therefore it isnot necessary for the border node to perform transmission of updateinformation to the source node every time the destination node shifts,so that it is possible to reduce the amount of processing, as comparedwith the twenty-sixth preferred embodiment of the present invention.

THE TWENTY-EIGHTH PREFERRED EMBODIMENT

[0269] A non border node according to a twenty-eighth preferredembodiment according to the present invention will now be explained withreference to FIG. 35. FIG. 35 is a block structure diagram of anessential portion of a non border node according to this twenty-eighthpreferred embodiment of the present invention. This non border nodeaccording to this twenty-eighth preferred embodiment of the presentinvention, as shown in FIG. 35, comprises a reachability advertisementsection 23 which dispatches a packet for checking reachability to aborder node which corresponds to an interface of self virtual node. Inother words, while with the twenty-fourth through the twenty-eighthpreferred embodiments of the present invention it was possible for thenon border nodes to perform transmission of reachability to specifiedborder nodes, by contrast, in this twenty-eighth preferred embodiment ofthe present invention, the non border nodes perform advertisement ofreachability to non specified border nodes within self virtual node. Bydoing this, in the processing by the non border nodes, it is sufficientfor them simply to dispatch reachability advertisement packets, so thatit is possible to alleviate the processing burden.

[0270] IP headers for advertisement are assigned to the reachabilityadvertisement packets, and these are set up so as to be destined for nonspecified border nodes. Furthermore, by writing the IP addresses of thenon border nodes which are the sources of dispatch into said IP headers,it is possible to check the reachability corresponding to the IPaddresses in the border nodes which receive said IP packets foradvertisement, since it is possible to specify their sources ofdispatch.

[0271] Next, a border node according to this twenty-eighth preferredembodiment of the present invention will be explained with reference toFIG. 36. FIG. 36 is a block structure diagram of an essential portion ofthis border node according to the twenty-eighth preferred embodiment.This border node according to the twenty-eighth preferred embodiment ofthe present invention comprises a reception section 24 for reachabilityadvertisement packets which receives packets for checking reachabilityfrom other nodes within self virtual node, an internal IP address groupinformation creation section 25 which summarizes the IP addresses ofsaid packets which have been received and creates internal IP addressgroup information which is related to nodes within self virtual node, aninformation synchronization section 26 which converts said internal IPaddress group information which has thus been created with other bordernodes within self virtual node, compensates them so that they areneither too great nor too small, and synchronizes them as internal IPaddress group information which has been unified for self virtual node,and an external advertisement section 27 which advertises this internalIP address group information which has thus been unified by saidinformation synchronization section 26 to the border node whichcorresponds to the interface with the other virtual node.

[0272]FIG. 37 shows the general concept of operation of thistwenty-eighth preferred embodiment of the present invention. A nonborder node (shown by the white circle) emits a packet for advertisingreachability. A border node (shown by hatching) which has received thispacket establishes synchronization of the internal IP address groupinformation between border nodes (as shown by the broken line), and,after having created unified internal IP address group information,advertises said internal IP address group information to the border nodeof the other virtual node.

[0273] Furthermore, as shown in FIG. 38, when advertisements are beingperformed from a plurality of border nodes within self virtual node tothe same border node within an other virtual node, since the contents ofthe advertisements are the same, there will be no problem whichever ofthe border nodes within self virtual node perform the advertisement,and, due to this, it is possible to eliminate unnecessaryadvertisements. In order to implement this concept, as shown in FIG. 39,the external advertisement section 27 comprises an advertisementimplementation node determination section 28 which decides whether ornot an advertisement path is available from an other border node withinself virtual node to the border node which corresponds to the interfaceof the other virtual node, and, when the result of this decision is“yes”, performs advertisement by one or another advertisement path ofself node or of said other border node to the border node whichcorresponds to the interface of said other virtual node.

THE TWENTY-NINTH PREFERRED EMBODIMENT

[0274] A border node according to a twenty-ninth preferred embodiment ofthe present invention will now be explained with reference to FIG. 40.FIG. 40 is a block structure diagram of an essential portion of a bordernode according to this twenty-ninth preferred embodiment of the presentinvention. This border node comprises: a reception section 24 forreachability advertisement packets which receives packets for checkingreachability from other nodes within self virtual node, an internal IPaddress group information creation section 25 which summarizes the IPaddresses of said packets which have been received and creates internalIP address group information which is related to nodes within selfvirtual node, and an external advertisement section 27 which advertisesthis internal IP address group information which has thus been createdto the border node which corresponds to the interface with the othervirtual node.

[0275] Thus, in this border node according to the twenty-ninth preferredembodiment of the present invention, the information synchronizationsection 26 of the twenty-eighth preferred embodiment of the presentinvention has been eliminated. By doing this, it is ventured to permitdisagreement of the internal IP address group information between bordernodes within the same virtual node. In other words, since it may happenthat the reachability with respect to some border node may differ evenfor border nodes within the same virtual node, by performingadvertisement of this kind of distinction, it becomes possible torecognize the border nodes through which it is not possible to establisha path by path computation.

THE THIRTIETH PREFERRED EMBODIMENT

[0276] A non border node according to a thirtieth preferred embodimentof the present invention will now be explained with reference to FIG.41. FIG. 41 is a block structure diagram of an essential portion of anon border node according to this thirtieth preferred embodiment of thepresent invention. This non border node according to the thirtiethpreferred embodiment of the present invention comprises a link costcomputation section 30 which computes individual link costs for aplurality of border nodes which correspond to said interface of selfvirtual node. In other words, it computes a link cost to each bordernode within self virtual node, based upon the information which has beenstored in the retention section 2 for information within self virtualnode.

[0277] The IP address notification section 29 transmits its own IPaddress by emitting a packet for checking reachability to the bordernode which corresponds to said interface for which, according to thecomputation results of this link cost computation section 30, the linkcost is the least.

[0278] By doing this, the border node is able to ascertain only the IPaddress of the non border node for which the link cost is the least, andaccordingly it is possible to reduce the amount of information whichneeds to be summarized and advertised.

THE THIRTY-FIRST PREFERRED EMBODIMENT

[0279] A non border node according to a thirty-first preferredembodiment of the present invention will now be explained with referenceto FIG. 41. FIG. 41 is a block structure diagram of an essential portionof a non border node according to this thirty-first preferred embodimentof the present invention, and is common with the thirtieth preferredembodiment. This non border node according to the thirty-first preferredembodiment of the present invention comprises a link cost computationsection 30 which computes individual link costs for a plurality ofborder nodes which correspond to said interface of self virtual node. Inother words, it computes a link cost to each border node within selfvirtual node, based upon the information which has been stored in theretention section 2 for information within self virtual node.

[0280] The IP address notification section 29 transmits its own IPaddress by emitting a packet for checking reachability to the bordernode which corresponds to said interface for which, according to thecomputation results of this link cost computation section 30, the linkcost is the n-th least in order (where n is a natural number).

[0281] By doing this, the border node is able to ascertain only the IPaddresses of the minority of non border nodes for which the link costsare the least in order, and accordingly it is possible to reduce theamount of information which needs to be summarized and advertised. Tocompare this thirty-first preferred embodiment of the present inventionwith the thirtieth preferred embodiment of the present inventiondescribed above, although it may happen that the amount of informationwhich needs to be summarized and advertised becomes greater, byappropriately varying the value of the natural number n, it is easilypossible to adjust the amount of information to an amount which theborder nodes can most easily deal with in every possible set ofcircumstances.

THE THIRTY-SECOND PREFERRED EMBODIMENT

[0282] A non border node according to a thirty-second preferredembodiment of the present invention will now be explained with referenceto FIG. 41. FIG. 41 is a block structure diagram of an essential portionof a non border node according to this thirty-second preferredembodiment of the present invention, and is common with the thirtiethand the thirty-first preferred embodiments. This non border nodeaccording to the thirty-second preferred embodiment of the presentinvention, as shown in FIG. 41, comprises a link cost computationsection 30 which computes individual link costs for a plurality ofborder nodes which correspond to said interface of self virtual node. Inother words, it computes a link cost to each border node within selfvirtual node, based upon the information which has been stored in theretention section 2 for information within self virtual node.

[0283] The IP address notification section 29 transmits its own IPaddress and summarized link cost information to the border node whichcorresponds to said interface for which, according to the computationresults of this link cost computation section 30, the link cost is then-th least in order (where n is a natural number), by emitting a packetfor checking reachability which includes information about said numberin order.

[0284] By doing this, the border node is able to ascertain only the IPaddresses of the minority of non border nodes for which the link costsare the least in order, and accordingly it is possible to reduce theamount of information which needs to be summarized and advertised. Tocompare this thirty-second preferred embodiment of the present inventionwith the thirtieth-first preferred embodiment of the present inventiondescribed above, it is possible to recognize the summary informationabout link cost by the information about the number in order of the linkcost. With summary information and the like, it is possible to alleviatethe amount of information which must be handled, as compared with thecase of dealing with complete link cost information.

[0285] It should be understood that, as shown in FIG. 42, this bordernode according to the thirty-second preferred embodiment of the presentinvention comprises: a reception section 32 for packets for checkingreachability, which receives packets for checking reachability whichinclude information to the effect that, from the other nodes within selfvirtual node, self node has the n-th smallest link cost with respect tosaid other nodes; an internal IP address group information creationsection 33 which summarizes for each of said n values the IP addressesof the packets which have been received by said reception section 32 forpackets for checking reachability, and creates internal IP address groupinformation related to nodes within self virtual node; and an externaladvertisement section 27 which advertises this internal IP address groupinformation which has thus been created by said internal IP addressgroup information creation section 33 to the border node whichcorresponds to the interface with the other virtual node.

THE THIRTY-THIRD PREFERRED EMBODIMENT

[0286] A non border node according to a thirty-third preferredembodiment of the present invention will now be explained with referenceto FIGS. 43 and 44. FIG. 43 is a block structure diagram of an essentialportion of a non border node according to this thirty-third preferredembodiment of the present invention. And FIG. 44 is a general conceptualfigure of the scope of level 1 of the non border node according to thisthirty-third preferred embodiment of the present invention. This nonborder node according to the thirty-third preferred embodiment of thepresent invention, as shown in FIG. 43, comprises an advertisementsection 1 which advertises information about links which are connectedto this link and link cost information about said links to the othernodes within self virtual node, and a retention section 2 forinformation within self virtual node which receives information aboutlinks within self virtual node and link information about the cost ofsaid links from other nodes within self virtual node, and stores saidinformation.

[0287] In other words, with this thirty-third preferred embodiment ofthe present invention, as shown in FIG. 44, normally, a non border node(shown by the white circle) only stores information relating to thesituation within self virtual node. By doing this, it is possible toreduce the amount of data which must be handled.

[0288] However, with this embodiment, since it is not possible toperform path computation all the way up to the destination which isanother virtual node, accordingly there is included a capture section 31for information within other virtual nodes, which, before performing thepath computation, requests and obtains, from a border node whichcorresponds to said interface, link information for between a bordernode which corresponds to an interface with self virtual node and aborder node which corresponds to an interface with a virtual node upon ahigher level, and link cost information for said link.

[0289] By doing this, the amount of information is reduced by, normally,only handling information within self virtual node, while, according torequirements, receiving information about the situation within othervirtual nodes, so that it is possible to reduce the amount ofinformation which must be handled within a fixed time.

THE THIRTY-FOURTH PREFERRED EMBODIMENT

[0290] A border node according to a thirty-fourth preferred embodimentof the present invention will now be explained with reference to FIGS.45 and 46. FIG. 45 is a block structure diagram of an essential portionof a border node according to this thirty-fourth preferred embodiment ofthe present invention. And FIG. 46 is a general conceptual figure of thescope of level 2 of the border node according to this thirty-fourthpreferred embodiment. This non border node according to thethirty-fourth preferred embodiment of the present invention, as shown inFIG. 45, comprises: an advertisement section 34 which advertises toborder nodes which correspond to interfaces upon the same level as selfnode link information about links upon the same level at self node whichhave been connected to self node, and link cost information for saidlinks; and a same level border node information retention section 35which receives, from border nodes which correspond to interfaces uponthe same level as self node, advertisements of link information forlinks between self node and border nodes which correspond to interfacesupon the same level as self node, and link cost information for saidlinks, and stores said information. In other words, with this non bordernode according to the thirty-fourth preferred embodiment of the presentinvention, as shown in FIG. 46, normally, the border nodes (shown byhatching) only store information between themselves and border nodesupon the same level as themselves. Due to this, it is possible to reducethe amount of data which must be handled.

[0291] However since, with this system, it is not possible to performpath computation for some destination which is in a virtual node on ahigher level than self node itself, there is incorporated a capturesection 36 for information within virtual nodes on higher levels, which,before the path computation, requests and receives link informationabout links with a border node which corresponds to an interface on ahigher level than self node, and link cost information about said links,from the border node which corresponds to said interface.

[0292] By doing this, it is possible to reduce the amount of informationwhich is to be handled within a fixed time by, normally, only handlinginformation between self node and border nodes which are upon the samelevel, while, according to requirements, receiving information about thesituation within virtual nodes which are upon higher levels than selfnode.

[0293] It should be understood that, by combining the non border nodeaccording to the thirty-third preferred embodiment of the presentinvention and the border node according to the thirty-fourth preferredembodiment of the present invention, it becomes possible to implement anembodiment in which, normally, nodes of each level only handleinformation between themselves and nodes upon the same level, while,according to requirements, they obtain and utilize information betweennodes on levels higher than themselves.

THE THIRTY-FIFTH PREFERRED EMBODIMENT

[0294] A thirty-fifth preferred embodiment of the present invention willnow be explained with reference to FIGS. 47 and 48. FIGS. 47 and 48 arefigures for explanation of this path search method according to thisthirty-fifth preferred embodiment of the present invention. In thisthirty-fifth preferred embodiment of the present invention, as a nonborder node, the non border node according to the thirty-third preferredembodiment of the present invention which was explained with referenceto FIG. 43 is employed. In other words, referring to the FIG. 47example, there are incorporated a capture section 31 for informationwithin other virtual nodes which requests and obtains link informationfor links within said virtual node and link cost information about saidlinks from the border node #7 which corresponds to the interface of thevirtual node to which the destination node #8 belongs, and a path searchsection which, in addition to the path which has already been searchedout to the border node #7 which corresponds to the interface with thevirtual node to which the destination node #8 belongs, based upon saidlink information and said link cost information which have been obtainedby said capture section 31 for information within other virtual nodes,as shown in FIG. 48, searches out a path from the border node #7 whichcorresponds to said interface to the destination node #8.

[0295] It should be understood that the operation of searching out apath from the source node #1 to the border node #7 is the same as thatexplained above with reference to the twenty-fourth preferred embodimentof the present invention.

[0296] Furthermore, for example, if the source node #1 desires toperform detailed path searching within the virtual node to which theborder nodes #5 and #6 belong, then the capture section 31 forinformation within other virtual nodes requests and obtains linkinformation for links within said virtual node and link cost informationabout said links from the border node #5 or the border node #6, and,based upon said link information and said link cost information which ithas received, searches out a path from self node within the virtual nodeto which border node #5 and the border node #6 belong.

[0297] By doing this, the source node #1 is able to perform detailedpath searching by obtaining information within any one of the virtualnodes.

THE THIRTY-SIXTH PREFERRED EMBODIMENT

[0298] A path search method according to a thirty-sixth preferredembodiment of the present invention will now be explained with referenceto FIGS. 48 through 50. FIG. 48 is a figure for explanation of this pathsearch method according to this thirty-sixth preferred embodiment of thepresent invention, and is common with the thirty-fifth preferredembodiment. FIG. 49 is a figure showing the overall block structure of anon border node according to this thirty-sixth preferred embodiment ofthe present invention. And FIG. 50 is a sequence diagram for explanationof the path search method according to this thirty-sixth preferredembodiment of the present invention.

[0299] With this path search method according to this thirty-sixthpreferred embodiment of the present invention, referring to the examplein FIG. 50, the source node #1 for path establishment comprises adestination node position search section 5 which specifies the virtualnode #B to which said destination node #8 belongs from the IP address ofthe destination node #8 for path establishment, based upon the externalIP address group information, and a path search section 37 which, basedupon link information for links between the border node #2 whichcorresponds to the interface with self virtual node and the border node#4 which corresponds to an interface with a virtual node which is on ahigher level than self virtual node, and upon link cost information forsaid links, notifies to the destination node #8 for path establishmentinformation which specifies on which level is the virtual node #A on thetopmost level for which path computation is possible from self node tothe border node #4 which corresponds to the interface, and the resultsof searching out paths from self node to the border node #4 whichcorresponds to said interface in order up to that one for which the linkcost is the n-th smallest, and the destination node #8, based upon saidinformation which has been notified, along with searching out a pathfrom self node to the border node #4 which corresponds to the interfaceof the virtual node #A on said topmost level for which path computationup to the border node #4 which corresponds to the interface from thesource node #1 is possible, also comprises a path search section 37which combines the results of searching out a path up to said n-th levelin said search results, and notifies the path for which the link cost isthe least to the search node #1 as the final path which has been found.

[0300] In other words, as shown in FIG. 50, the source node #1 specifiesthe position of the destination node #8 with the destination nodeposition search section 5 (in the step 1), searches out a path to thevirtual nodes #4 and #9 upon the topmost level for which computation bythe path search section 37 is possible (in the step 2), and notifiesthese search results to the destination node #8 (in the step 3). In thedestination node #8, a path to the virtual nodes #4 and #9 is searchedout by the path search section 37 (in the step 4), and, by adding thepath to the virtual nodes #4 and #9 from the source node #1 which hasbeen notified from the source node #1, selects the path for which thelink cost becomes the minimum (in the step 5), and notifies theseselection results to the source node #1 (in the step 6). In the sourcenode #1, an LSP to the destination node #8 is established based uponthis notification (in the step 7). It should be understood that thisestablishment of an LSP may also be performed from the destination node#8 (in the step 8). If the LSP is to be established from the destinationnode #8, it is possible to eliminate the step 6.

[0301] The beneficial feature of this path search method according tothis thirty-sixth preferred embodiment of the present invention is that,in a case such as when, for example, it is necessary to establish alarge number of LSPs from a single source node to a large number ofdestination nodes all together, and it is difficult for the side of thesource node to bear the entire burden which is required to establish theLSPs, by sharing out the burden which is required for the path searchingto the sides of the destination nodes, it is thereby possible toalleviate the burden which is imposed upon the source node by this pathsearching procedure.

THE THIRTY-SEVENTH PREFERRED EMBODIMENT

[0302] The establishment of a border node in a thirty-ninth preferredembodiment of the present invention will now be explained with referenceto FIGS. 51 through 53. FIGS. 51 and 52 are figures for explanation ofthe definition of a border node according to this thirty-seventhpreferred embodiment of the present invention, and is common with thethirty-seventh preferred embodiment. And FIG. 53 is a block structuraldiagram of an essential portion of a node according to thisthirty-seventh preferred embodiment of the present invention. Since thelayered network according to this thirty-seventh preferred embodiment ofthe present invention is implemented as a multi layer network, Lambdapaths, TDM-LSPs, and packet paths are mixed together within links whichare established between the virtual nodes.

[0303] This border node according to this thirty-seventh preferredembodiment of the present invention, within a virtual node which hasbeen created, exercises autonomously a function as a border node incorrespondence with the layer of a LSP which has been establishedbetween virtual nodes which are adjacent. For example, in FIG. 51, it isa Lambda path upon the Lambda layer which is established between virtualnodes which are adjacent. Accordingly, an optical cross connect devicewhich corresponds to the node 2 is established as a border node.Furthermore, in FIG. 52, it is a packet path upon the IP layer which isestablished between virtual nodes which are adjacent. Accordingly, arouter which corresponds to the node 1 is established as a border node.In this manner, the termination point of an LSP between virtual nodeswhich are adjacent is established as a border node of the virtual node.

[0304] In this border node according to this thirty-seventh preferredembodiment of the present invention, as shown in FIG. 53, there isprovided a termination point decision section 38, and this terminationpoint decision section 38: refers to the link information which has beenstored in the retention section 3 for information within other virtualnodes and makes a decision as to whether or not a link which connectsself virtual node and an other virtual node is connected to self node;if, according to the result of this decision, the link which connectsself virtual node and an other virtual node is connected to self node,makes a decision as to whether or not self node corresponds to thetermination point for the layer of the LSP which has been establishedupon said link; and if, according to the result of this decision, selfnode corresponds to said termination point, recognizes that self node isa border node which corresponds to said interface, and issues a commandto the interface functional section 39 to exercise a function whichcorresponds to the interface.

THE THIRTY-EIGHTH PREFERRED EMBODIMENT

[0305] A thirty-eighth preferred embodiment of the present inventionwill now be explained with reference to FIGS. 54 and 55. FIG. 54 is afigure for explanation of a method of dividing up into virtual nodesaccording to this thirty-eighth preferred embodiment of the presentinvention. And FIG. 55 is a block structural diagram of an essentialportion of a node according to this thirty-eighth preferred embodimentof the present invention.

[0306] When dividing the nodes up into virtual nodes, it is inevitablethat division into different nodes will be performed for nodes betweenwhich no link has been established from the beginning. Although thereare virtual nodes which have been divided up by doing this, with thisthirty-eighth preferred embodiment of the present invention, as shown inFIG. 54, during the network management process, for nodes within thesame virtual node between which a link is established, if the resourcesare entirely utilized by other nodes, so that in practical terms thereachability has failed, (shown by the X signs in the figures), thenthey are divided up into different virtual nodes, thus being treated asthough the link did not exist.

[0307] By doing this, simply, by comparison with the case of divisioninto virtual nodes only according to the presence or absence of links,it is possible to construct a layered network which reflects thepresence or absence of reachability in practice, so that it is possibleto perform path searching and packet transmission at high accuracy andwith good efficiency.

[0308] This node according to this thirty-eighth preferred embodiment ofthe present invention, as shown in FIG. 55, comprises a resourceutilization state monitoring section 40 which observes the state ofutilization of resources related to self node, and if, based upon theresults of observation by this resource utilization state monitoringsection 40, availability of resources for use in data transmission toother nodes within self virtual node disappears, and self nodecorresponds to said interface, outputs a command to the node functionalsection 41, and, along with exercising a function as a node whichbelongs to an other virtual node of level 1 to which self node has beenconnected, also updates the information about the virtual node to whichself node belongs, which has been stored in the virtual node informationretention section 42, along with change of said associated virtual node.

[0309] Furthermore, the virtual node information retention section 42,along with advertising the details of updates, also, when such anadvertisement has been received from an other node, updates theinformation for the virtual note to which self node belongs, based uponsaid advertisement.

THE THIRTY-NINTH PREFERRED EMBODIMENT

[0310] A thirty-ninth preferred embodiment of the present invention willnow be explained with reference to FIGS. 54 and 56. FIG. 54 is a figurefor explanation of a method of dividing up into virtual nodes accordingto this thirty-ninth preferred embodiment of the present invention, andis common with the thirty-eighth preferred embodiment. And FIG. 56 is ablock structural diagram of an essential portion of a node according tothis thirty-ninth preferred embodiment of the present invention.

[0311] When dividing the nodes up into virtual nodes, it is inevitablethat division into different nodes will be performed for nodes betweenwhich no link has been established from the beginning. Although thereare virtual nodes which have been divided up by doing this, with thisthirty-ninth preferred embodiment of the present invention, as shown inFIG. 54, during the network management process, for nodes within thesame virtual node between which a link is established, if the link costhas exceeded a threshold value, (shown by the X signs in the figures),then they are divided up into different virtual nodes, thus beingtreated as though the link did not exist.

[0312] By doing this, simply, by comparison with the case of divisioninto virtual nodes only according to the presence or absence of links,it is possible to construct a layered network which reflects theexcellence or poorness of reachability in practice, so that it ispossible to perform path searching and packet transmission at highaccuracy and with good efficiency.

[0313] This node according to this thirty-ninth preferred embodiment ofthe present invention, as shown in FIG. 56, comprises a link costmonitoring section 43 which observes the link cost related to self node,and if, based upon the results of observation by this link costmonitoring section 43, the cost of links for use in data transmission toother nodes within self virtual node becomes greater than a thresholdvalue, and self node corresponds to said interface, outputs a command tothe node functional section 44, and, along with exercising a function asa node which belongs to an other virtual node of level 1 to which selfnode has been connected, also updates the information about the virtualnode to which self node belongs, which has been stored in the virtualnode information retention section 42, along with change of saidassociated virtual node.

[0314] Furthermore, the virtual node information retention section 42,along with advertising the details of these updates, also, when such anadvertisement has been received from an other node, updates theinformation for the virtual note to which self node belongs, based uponsaid advertisement.

THE FORTIETH PREFERRED EMBODIMENT

[0315] The node according to the fortieth preferred embodiment of thepresent invention will now be explained with reference to FIG. 57. FIG.57 is a block structural diagram of an essential portion of self nodeaccording to the fortieth preferred embodiment of the present invention.The node according to the fortieth preferred embodiment of the presentinvention is a device which combines the nodes of the nodes according tothe thirty-eighth and the thirty-ninth preferred embodiments of thepresent invention. In other words, it commands the node functionalsection 45 to initiate its own functions by referring to both theresource utilization state information due to the resource utilizationstate monitoring section 40 and also the link cost information withinthe virtual node due to the link cost monitoring section 43. By doingthis, it is possible to implement division into virtual nodes whileaccruing the benefits of both the thirty-eighth preferred embodiment andalso the thirty-ninth preferred embodiment of the present invention.

THE FORTY-FIRST PREFERRED EMBODIMENT

[0316] The forty-first preferred embodiment of the present invention isa preferred embodiment of a network control device which controls thelayered network all together. Although, in the explanation of theforty-first through the forty-fourth preferred embodiments of thepresent invention, the explanation will be made in terms of only onenetwork control device being provided to a layered network, if thefollowing explanation is applied to only a part of the layered network,it would also be possible to explain in the same manner a mode ofimplementation which controlled the entire layered network using aplurality of network control devices. In the explanation of thisforty-first preferred embodiment of the present invention, theestablishment of a border node will be explained with reference to FIGS.51, 52, and 58. FIGS. 51 and 52 are figures for explanation of thedefinition of a border node. And FIG. 58 is a block structure diagramshowing an essential portion of the network control device according tothe forty-first preferred embodiment of the present invention. Since thelayered network of this forty-first preferred embodiment is implementedas a multi layer network, Lambda paths, TDM-LSPs, and packet paths aremixed together within links which are established between the virtualnodes.

[0317] The network control device establishes a border nodecorresponding to the layer of an LSP which has been established betweenadjacent virtual nodes within a virtual node which has been created. Forexample, in FIG. 51, it is a Lambda path upon the Lambda layer which isestablished between adjacent virtual nodes. Accordingly, an opticalcross connect device which corresponds to a node 2 is established as aborder node. Furthermore, in FIG. 52, it is a packet path upon the IPlayer which is established between adjacent virtual nodes. Accordingly,a router which corresponds to a node 1 is established as a border node.In this manner, the termination point of an LSP between adjacent virtualnodes is established as a border node of self virtual node.

[0318] In the network control device according to this forty-firstpreferred embodiment of the present invention, as shown in FIG. 58,there is provided a node type database 46, in which information relatedto the types of nodes which are provided within the network isaccumulated. And a border node establishment section 47 refers to selfnode type database 46, recognizes the types of the nodes within eachvirtual node, and determines upon a node to be established as a bordernode corresponding to the layer of a link between adjacent virtualnodes, and dispatches an establishment command for said node. The nodewhich has received this establishment command recognizes itself as aborder node, and accordingly exercises a function as a border node.

THE FORTY-SECOND PREFERRED EMBODIMENT

[0319] A network control device according to a forty-second preferredembodiment of the present invention will now be explained with referenceto FIGS. 54 and 59. FIG. 54 is a figure for explanation of the method ofdividing up into virtual nodes of this forty-second preferred embodimentof the present invention, and is common with the thirty-eighth and thethirty-ninth preferred embodiments of the present invention. And FIG. 59is a block structure diagram showing an essential portion of the networkcontrol device according to this forty-second preferred embodiment ofthe present invention.

[0320] When dividing up a node into virtual nodes, it is inevitable todivide nodes between which no link has been established from thebeginning into different virtual nodes. Although there are virtual nodeswhich have been divided up by doing this, in the forty-second preferredembodiment of the present invention, as shown in FIG. 54, in the networkmanagement process, for nodes within the same virtual node between whicha link is established, if the relevant resources are completely used byother nodes, and in practice their mutual reachability has disappeared(shown in the figure by a X sign), then they are considered as beingones between which no link exists, and accordingly they are divided upinto different virtual nodes.

[0321] By doing this, simply, to compare with the case of dividing upinto virtual nodes merely according to the presence or absence of links,it is possible to construct a layered network which reflects the actualpresence or absence of mutual reachability, and thereby it is possibleto perform path search and packet transmission with high accuracy andgood efficiency.

[0322] The network control device according to this forty-secondpreferred embodiment of the present invention, as shown in FIG. 59,comprises a resource utilization state monitoring section 48 whichobserves the resource utilization state of each node, and a virtual nodeseparation control section 49 refers to the resource utilization statemonitoring section 48, and commands each of the nodes to divide into newvirtual nodes as required. In a node which has received this command, itrenews the information about the virtual node to which it itselfbelongs, and then exercises a function as a node within the new virtualnode.

THE FORTY-THIRD PREFERRED EMBODIMENT

[0323] A network control device according to a forty-third preferredembodiment of the present invention will now be explained with referenceto FIGS. 54 and 60. FIG. 54 is a figure for explanation of the method ofdividing up into virtual nodes of this forty-third preferred embodimentof the present invention, and is common with the thirty-eighth, thethirty-ninth, and the forty-second preferred embodiments of the presentinvention. And FIG. 60 is a block structure diagram showing an essentialportion of the network control device according to this forty-thirdpreferred embodiment of the present invention.

[0324] When dividing up a node into virtual nodes, it is inevitable todivide nodes between which no link has been established from thebeginning into different virtual nodes. Although there are virtual nodeswhich have been divided up by doing this, in this forty-third preferredembodiment of the present invention, as shown in FIG. 54, in the networkmanagement process, for nodes within the same virtual node between whicha link is established, if the link cost has exceeded a threshold value(shown in the figure by an X sign), then they are considered as beingones between which no link exists, and accordingly they are divided upinto different virtual nodes.

[0325] By doing this, simply, to compare with the case of dividing upinto virtual nodes merely according to the presence or absence of links,it is possible to construct a layered network which reflects themagnitude of the actual mutual reachability, and thereby it is possibleto perform path search and packet transmission with good efficiency.

[0326] The network control device according to this forty-thirdpreferred embodiment of the present invention, as shown in FIG. 60,comprises a link cost monitoring section 50 which observes the link costof each node, and a virtual node separation control section 51 refers tothe link cost monitoring section 50, and commands each of the nodes todivide into new virtual nodes as required. In a node which has receivedthis command, it renews the information about the virtual node to whichit itself belongs, and then exercises a function as a node within thenew virtual node.

[0327] By applying the virtual node division method which has beenexplained with reference to this forty-third preferred embodiment of thepresent invention, it becomes possible to keep the link cost within eachvirtual node constant. Accordingly, there is the benefit that therequirement for advertising the link cost information to the exteriordisappears. For example, the value of the threshold value may be takenas the link cost value of the virtual node for which the link cost isthe least, so that the link cost of each virtual node remains constant.

THE FORTY-FOURTH PREFERRED EMBODIMENT

[0328] The network control device according to the forty-fourthpreferred embodiment of the present invention will now be explained withreference to FIG. 61. FIG. 61 is a block structure diagram showing anessential portion of this network control device according to theforty-fourth preferred embodiment of the present invention. This networkcontrol device according to the forty-fourth preferred embodiment of thepresent invention is a combination of the network control devicesaccording to the forty-second and the forty-third preferred embodimentsof the present invention. In other words, the virtual node separationcontrol section 52 commands the separation into virtual nodes byreferring to both of the resource utilization state information betweenthe nodes which is produced by the resource utilization state monitoringsection 48 and also to the link cost information within the virtualnodes which is produced by the link cost monitoring section 50. By doingthis, it is possible to implement separation into virtual nodes whileobtaining the benefits of both the forty-second preferred embodiment andalso the forty-third preferred embodiment of the present invention.

What is claimed is:
 1. A layered network node which is provided in anetwork consisting of one or a plurality of layers, comprising: a meansfor mutually interchanging with other nodes information about thepresent node and links which are connected to the present node(hereinafter termed “link state information); a means for storing linkstate information for one or for all of the nodes within said networkwhich has been obtained by this interchanging means; a means forselecting a path for an LSP of one or a plurality of types of layer,based upon link state information which has been stored in said storingmeans according to an LSP establishment request; and a means forchanging the path which has been selected and established by thisselection means, according to an LSP change request, based upon linkstate information which has been stored in said storing means; whereinthe network to which said node belongs is a layered network which isbuilt up by: dividing up into cells which are constituted by a pluralityof nodes; defining these cells as virtual nodes; if links exist whichconnect the interiors of the virtual nodes and the exterior, definingthe contact points between these interiors of the virtual nodes and theexterior as interfaces of the virtual nodes; further dividing up thevirtual network which has been constituted by the virtual nodes intocells; making them into virtual nodes; further dividing them up intocells; the virtual network which has been made into virtual nodes isdefined as a network of a higher level with respect to the initialvirtual network; and by performing the above described operation ofdivision into cells and making into virtual nodes once or a plurality oftimes; and comprising a link state database which accumulates link stateinformation which is advertised from other nodes within the virtual nodeto which self node belongs or from other virtual nodes; and the nodeswhich fulfill a function of interfacing with nodes within the virtualnode or with the exterior of the virtual node are defined as bordernodes, and comprises: a link state abstraction section comprising ameans for, when the present node is positioned at this border node,creating interface information for the exterior of the virtual nodebased upon link state information interior to the virtual node; and anadvertisement section which advertises said interface information whichhas been created to the exterior of the virtual node.
 2. A layerednetwork node according to claim 1, further comprising a means forrecognizing a link group, among a plurality of links which mutuallyconnect virtual nodes together, which connects between the same virtualnode; and a processing means for treating the links which are includedwithin the link group which has been recognized by this recognitionmeans as a single virtual link.
 3. A layered network node according toclaim 1, further comprising: a means for recognizing a first link group,among a plurality of which mutually connect virtual nodes together,which connects between the same virtual node; a means for furtherclassifying the first link group which has been recognized by saidrecognition means into second link groups which possess the sameswitching capability; and a processing means for treating the linkswhich are included within the second link group which has beenclassified by said classification means as a single virtual link.
 4. Alayered network node according to claim 1, wherein said link stateabstraction section comprises a switching capability allotment means forperforming allotment of the switching capability within the virtual nodeto which the present node belongs by a link which is connected to thepresent node to a link which corresponds to an interface which connectsthe virtual node and moreover to which the present node belongs and theexterior; and said interface information is information about theswitching capability which has been allotted to said interfaces by saidswitching capability allotment means.
 5. A layered network nodeaccording to claim 1, wherein said link state abstraction sectioncomprises: a switching capability allotment means for performingallotment of the switching capability within the virtual node to whichthe present node belongs by a link which is connected to the presentnode to a link which corresponds to an interface which connects thevirtual node to which the present node belongs and the exterior; and acost allotment means for allotting a transmission cost to each switchingcapability which has been allotted by said switching capabilityallotment means; and said interface information is information about theswitching capability which has been allotted to said interfaces by saidswitching capability allotment means, and information about thetransmission costs which have been allocated to the switchingcapabilities of said interfaces by said cost allotment means.
 6. Alayered network node according to claim 4 or claim 5, wherein saidinformation about the switching capability which has been allotted tosaid interfaces is created in correspondence with each layer of an LSPwhich can be established between the present node as a border node or avirtual border node, and another border node or another virtual bordernode which belongs within the same virtual node.
 7. A layered networknode according to claim 4 or claim 5, wherein said information about theswitching capability which has been allotted to said interfaces isinformation which is related to the switching capability of a bordernode or a virtual border node to which the link which constitutes saidinterface is directly connected.
 8. A layered network node according toclaim 1, wherein said advertisement section comprises a means forperforming an advertisement to the exterior of the virtual node eachtime a change in switching capability of said border node occurs.
 9. Alayered network node according to claim 1, wherein said advertisementsection comprises a means for performing an advertisement to theexterior of the virtual node at a fixed interval.
 10. A layered networknode according to claim 5, wherein said information about transmissioncost is generated as the reciprocal of the total number of interfaceswhich are not in use to which switching capability of said layer whichis included in the virtual node is allotted.
 11. A layered network nodeaccording to claim 5, wherein said information about transmission costis generated, in relation to the number of interfaces to which switchingcapability of said layer which is included in the virtual node isallotted which are in use, and the total number of interfaces, as thenumber of interfaces in use divided by the total number of interfaces.12. A layered network node according to claim 5, wherein saidinformation about transmission cost, between a border node within thevirtual node and another border node which belongs to the same bordernode as said border node, is information which is determined for eachlayer of the LSP which is established as the cost when establishing aLSP of any layer.
 13. A layered network node according to claim 12,wherein said cost allotment means comprises a means for calculating acost value of the path for which the value, which is obtained by adding,along the path when establishing an LSP between a border node within thevirtual node and another border node which belongs to the same bordernode as said border node, the link cost of the link and the node cost ofthe node or the virtual node, becomes minimum.
 14. A layered networknode according to claim 12, wherein said cost is the value which isobtained by adding the link cost of the link and the node cost of thenode or the virtual node along the path of the minimum number of hopswhich is established between a border node within the virtual node andanother border node which belongs to the same border node as said bordernode; and comprising a means for, if there exists a plurality of saidpaths of the minimum number of hops, selecting from among cost valuecandidates which are aggregates of a plurality of values which areobtained by said addition, as the cost value, that one for which itsvalue becomes minimum.
 15. A layered network node according to claim 13or claim 14, wherein said value which is obtained by said addition isthe reciprocal of the number of interfaces which are not in use to whichswitching capability of said layer which is included in the virtualnodes along said path is allotted.
 16. A layered network node accordingto claim 13 or claim 14, wherein said value which is obtained by saidaddition is given, in relation to the number of interfaces to whichswitching capability of said layer which is included in the nodes alongsaid path is allotted which are in use, and the total number ofinterfaces, by the number of interfaces used divided by the total numberof interfaces.
 17. A layered network node according to claim 5 or claim12, wherein a node which corresponds to an interface of a virtual nodecomprises a means for computing information about said transmissioncost, or said cost, based upon said link state information at a timeinterval which is fixed in advance.
 18. A layered network node accordingto claim 5 or claim 12, wherein a node which corresponds to an interfaceof a virtual node comprises a means for computing information about saidtransmission cost, or said cost, based upon said link state information,whenever change of the utilization state of the interface within thevirtual node is notified by advertisement of link state information andthe utilization state of the interface changes.
 19. A network comprisinga layered network node according to claim
 1. 20. A method for layeredpath selection when establishing an LSP of any layer within a networkwhich comprises a layered network node according to claim 1, in whichprocedures are executed of: when selecting a path from a source node toa destination node, deciding, by referring to said link state databaseof the lowest level 1, whether or not, among said virtual nodes of level1, the destination node is present within a virtual node which includesthe source node; if the source node and the destination node are notpresent within the same virtual node, deciding, by referring to saidlink state database of the next higher level 2, whether or not thedestination node is present within a virtual node of said level 2 whichincludes the source node; by repeating this decision until the sourcenode and the destination node are included within the same virtual node,selecting a virtual node of a level N (where N is a natural number)which includes both the source node and the destination node; whenselecting a path of level N from the source node to the destination nodewithin self virtual node of level N which has been selected, selectingthe path selection of a virtual node group which is included within saidvirtual node of level N which has been selected by said selection meansof said level N based upon said link state database of level N; whenfurther selecting a path of the next lowest level (N-1) from the sourcenode to the destination node from among the virtual nodes which areincluded in this path of level N which has been selected, selecting bysaid selection means of said level (N-1) based upon said link statedatabase of the next lowest level (N-1) than said virtual node which hasbeen selected; and by repeating this until the lowest level 1, selectinga path from the source node to the destination node.
 21. A method forlayered path selection when establishing an LSP of any layer within anetwork which comprises a layered network node according to claim 1, inwhich procedures are executed of: when selecting a path from a sourcenode to a destination node, in a network which is made up from virtualnodes of a topmost level N, deciding, by referring to said link statedatabase of said level N, whether or not the source node and thedestination node are present within the same virtual node; if the sourcenode and the destination node are present within the same virtual node,deciding, by referring to said link state database of the next lowerlevel (N-1) within self virtual node, whether or not the source node andthe destination node are present within the same virtual node in thenetwork of the next lower level (N-1) within self virtual node;selecting a virtual node of the level (N-k) which includes both thesource node and the destination node, by repeating this decision untilthe source node and the destination node are included within differentvirtual nodes, and selecting the virtual node of the next highest level(N-k) thereto (where k is a natural number); when selecting a path oflevel (N-k) from the source node to the destination node within selfvirtual node, selecting the path selection of a virtual node group whichis included within said virtual node of level (N-k) which has beenselected by said selection means of said level (N-k) based upon saidlink state database of said level (N-k); when further selecting a pathof the next lowest level (N-k-1) from the source node to the destinationnode from among the virtual nodes which are included in this path oflevel (N-k) which has been selected, selecting by said selection meansof said level (N-k-1) based upon said link state database of the nextlowest level (N-k-1) than said virtual node which has been selected; andby repeating this until the lowest level 1, selecting a path from thesource node to the destination node.
 22. A layered path selection methodaccording to claim 20 or claim 21, wherein, for a virtual node of alower level than the level which includes both said source node and saiddestination node, the computation for selecting the path within thepresent node is performed by that border node, among the border nodeswhich are included within self virtual node, which is allotted as aninput-output interface of said path.
 23. A layered path selection methodaccording to claim 20 or claim 21, wherein, for a virtual node of alower level than the level which includes both said source node and saiddestination node, the computation for selecting the path within thepresent node is performed by that border node, among the border nodeswhich are included within self virtual node, which is determined inadvance as a representative node.
 24. A program which, by beinginstalled upon an information processing device, causes said informationprocessing device, when establishing an LSP of any layer within anetwork which comprises a layered network node according to claim 1, toexecute procedures of: when selecting a path from a source node to adestination node, deciding, by referring to said link state database ofthe lowest level 1, whether or not, among said virtual nodes of level 1,the destination node is present within a virtual node which includes thesource node; if the source node and the destination node are not presentwithin the same virtual node, deciding, by referring to said link statedatabase of the next higher level 2, whether or not the destination nodeis present within a virtual node of said level 2 which includes thesource node; by repeating this decision until the source node and thedestination node are included within the same virtual node, selecting avirtual node of a level N (where N is a natural number) which includesboth the source node and the destination node; when selecting a path oflevel N from the source node to the destination node within self virtualnode of level N which has been selected, selecting the path selection ofa virtual node group which is included within said virtual node of levelN which has been selected by said selection means of said level N basedupon said link state database of level N; when further selecting a pathof the next lowest level (N-1) from the source node to the destinationnode from among the virtual nodes which are included in this path oflevel N which has been selected, selecting by said selection means ofsaid level (N-1) based upon said link state database of the next lowestlevel (N-1) than said virtual node which has been selected; and byrepeating this until the lowest level 1, selecting a path from thesource node to the destination node.
 25. A program which, by beinginstalled upon an information processing device, causes said informationprocessing device, when establishing an LSP of any layer within anetwork which comprises a layered network node according to claim 1, toexecute procedures of: when selecting a path from a source node to adestination node, in a network which is made up from virtual nodes of atopmost level N, deciding, by referring to said link state database ofsaid level N, whether or not the source node and the destination nodeare present within the same virtual node; if the source node and thedestination node are present within the same virtual node, deciding, byreferring to said link state database of the next lower level (N-1)within self virtual node, whether or not the source node and thedestination node are present within the same virtual node in the networkof the next lower level (N-1) within self virtual node; selecting avirtual node of the level (N-k) which includes both the source node andthe destination node, by repeating this decision until the source nodeand the destination node are included within different virtual nodes,and selecting the virtual node of the next highest level (N-k) thereto(where k is a natural number); when selecting a path of level (N-k) fromthe source node to the destination node within self virtual node,selecting the path selection of a virtual node group which is includedwithin said virtual node of level (N-k) which has been selected by saidselection means of said level (N-k) based upon said link state databaseof said level (N-k); when further selecting a path of the next lowestlevel (N-k-1) from the source node to the destination node from amongthe virtual nodes which are included in this path of level (N-k) whichhas been selected, selecting by said selection means of said level(N-k-1) based upon said link state database of the next lowest level(N-k-1) than said virtual node which has been selected; and by repeatingthis until the lowest level 1, selecting a path from the source node tothe destination node.
 26. A recording medium which can be read in bysaid information processing device, upon which is recorded a programaccording to claim 24 or claim
 25. 27. A node which constitutes avirtual node of level 1 in a layered network which has been defined bydividing up the nodes which make up the network into cells each made upfrom one or a plurality of said nodes and defining these cells asvirtual nodes of level 1, so that these virtual nodes of level 1constitute a virtual network of level 1, further dividing up thesevirtual nodes of level 1 which constitute said virtual network of level1 into cells which are constituted by one or a plurality of virtualnodes, so as to constitute virtual nodes of level 2, and constituting alayered network by virtual networks of levels 1 through N which havebeen built up by performing the process of dividing into cells andmaking into virtual nodes in this manner once or a plurality N of times,and by, if a link exists in said layered network which connects betweendifferent virtual nodes of the same level or of different levels,defining a node which corresponds to the point of contact between theinterior of the virtual node upon this link and the exterior as aninterface, so that, when the highest level virtual node to which saidinterface is related is of level M (where M(≦N), said interface servesas a plurality of hierarchical interfaces of level 1 through level M,comprising: a means for advertising to an other node within self virtualnode link information about a link which has been connected to self nodeand link cost information for said link; a means for receiving, from another node within self virtual node, said advertisement of linkinformation within self virtual node and link cost information for saidlink, and storing said information; and a means for receiving, from anode which corresponds to said interface within self virtual node, saidadvertisement of link information between said node and a node whichcorresponds to an interface with a virtual node of level 2 or greater,and link cost information for said link, and storing said information.28. A node according to claim 27, further comprising: a means fortransmitting its own IP address to a node which corresponds to aninterface of self virtual node; and a means for storing external IPaddress group information, which is information about an IP address ofan other node which belongs to a virtual node other than self virtualnode, and about the virtual node to which said IP address belongs, whichhave been transmitted from the node which corresponds to said interface.29. A node according to claim 27, further comprising: a means fortransmitting its own IP address to a node which corresponds to aninterface of self virtual node; and a means for requesting andobtaining, from the node which corresponds to said interface, externalIP address group information, which is information about an IP addressof an other node which belongs to a virtual node other than self virtualnode, and about the virtual node to which said IP address belongs.
 30. Anode according to claim 27, further comprising: a means for transmittingits own IP address and link cost information between itself and a nodewhich corresponds to an interface with self virtual node to the nodewhich corresponds to said interface; and a means for storing external IPaddress group information, which is information about an IP address ofan other node which belongs to a virtual node other than self virtualnode, and about the virtual node to which said IP address belongs, whichhas been transmitted from the node which corresponds to said interface,and link cost information from the node which corresponds to saidinterface to said other node, in correspondence to the IP address ofsaid other node.
 31. A node according to claim 27, further comprising: ameans for transmitting its own IP address and link cost informationbetween itself and a node which corresponds to an interface with selfvirtual node to the node which corresponds to said interface; and ameans for requesting and obtaining, from the node which corresponds tosaid interface, designates the IP address of said other node, externalIP address group information, which is information about an IP addressof an other node which belongs to a virtual node other than self virtualnode, and about the virtual node to which said IP address belongs, andlink cost information from the node which corresponds to said interfaceto said other node.
 32. A node according to claim 27, further comprisinga means for dispatching a packet for checking reachability to the nodewhich corresponds to said interface of self virtual node.
 33. A nodeaccording to claim 32, further comprising a means for computingrespective link costs for nodes which correspond to a plurality of saidinterfaces of said virtual node, wherein said dispatching meanscomprises a means for dispatching a packet for checking reachability tothe node which corresponds to said interface for which the link cost isthe least, according to the results of computation by this computationmeans.
 34. A node according to claim 32, further comprising a means forcomputing respective link costs for nodes which correspond to aplurality of said interfaces of said virtual node, wherein saiddispatching means comprises a means for dispatching packets for checkingreachability to the nodes which correspond to said interfaces for whichthe link cost, according to the results of computation by thiscomputation means, is the smallest in order until the nth, where n is anatural number.
 35. A node according to claim 32, further comprising ameans for computing respective link costs for nodes which correspond toa plurality of said interfaces of said virtual node, wherein saiddispatching means comprises a means for dispatching packets for checkingreachability to the nodes which correspond to said interfaces for whichthe link cost, according to the results of computation by thiscomputation means, is the smallest in order until the nth (where n is anatural number), said packets including information about said order.36. A node which constitutes a virtual node of level 1 in a layerednetwork which has been defined by dividing up the nodes which make upthe network into cells each made up from one or a plurality of saidnodes and defining these cells as virtual nodes of level 1, so thatthese virtual nodes of level 1 constitute a virtual network of level 1,further dividing up these virtual nodes of level 1 which constitute saidvirtual network of level 1 into cells which are constituted by one or aplurality of virtual nodes, so as to constitute virtual nodes of level2, and constituting a layered network by virtual networks of levels 1through N which have been built up by performing the process of dividinginto cells and making into virtual nodes in this manner once or aplurality of times, and by, if a link exists in said layered networkwhich connects between different virtual nodes of the same level or ofdifferent levels, defining a node which corresponds to the point ofcontact between the interior of the virtual node upon this link and theexterior as an interface, so that, when the highest level virtual nodeto which said interface is related is of level M (where M(≦N), saidinterface serves as a plurality of hierarchical interfaces of level Ithrough level N, comprising: a means for advertising link informationabout a link which has been connected to self node to an other nodewithin self virtual node and link cost information for said link; and ameans for receiving said advertisement of link information within selfvirtual node and link cost information for said link from an other nodewithin self virtual node, and storing said information.
 37. A nodeaccording to claim 36, further comprising a means for, ahead of pathcomputation, requesting and obtaining, from said node which correspondsto said interface, link information between a node which corresponds tothe interface with self virtual node and a node which corresponds to aninterface with a virtual node of level 2 or higher, and link costinformation for said link.
 38. A node which constitutes a virtual nodeof level 1 in a layered network which has been defined by dividing upthe nodes which make up the network into cells each made up from one ora plurality of said nodes and defining these cells as virtual nodes oflevel 1, so that these virtual nodes of level 1 constitute a virtualnetwork of level 1, further dividing up these virtual nodes of level 1which constitute said virtual network of level 1 into cells which areconstituted by one or a plurality of virtual nodes, so as to constitutevirtual nodes of level 2, and constituting a layered network by virtualnetworks of levels 1 through N which have been built up by performingthe process of dividing into cells and making into virtual nodes in thismanner once or a plurality of times, and by, if a link exists in saidlayered network which connects between different virtual nodes of thesame level or of different levels, defining a node which corresponds tothe point of contact between the interior of the virtual node upon thislink and the exterior as an interface, so that, when the highest levelvirtual node to which said interface is related is of level M (whereM≦N), said interface serves as a plurality of hierarchical interfaces oflevel 1 through level N, comprising, if self node itself corresponds tosaid interface: a means for advertising to an other node within selfvirtual node link information about a link within self virtual nodewhich has been connected to self node and link cost information for saidlink, and link information for a link with a node which corresponds toan interface of another virtual node which has been connected to selfnode, and link cost information for said link; a means for receiving,from an other node within self virtual node, said advertisement of linkinformation within self virtual node and link cost information for saidlink, and storing said information; and a means for receiving, from anode which corresponds to said interface with another virtual node,advertisement of link information with a node which corresponds to saidinterface of a higher level, and link cost information for said link,and storing said information.
 39. A node according to claim 38, furthercomprising: a means for gathering together and storing IP addressinformation from other nodes within self virtual node; a means foradvertising the IP address information which has been gathered togetherby this gathering together and storing means to a node which correspondsto an interface of another virtual node; and a means for storingexternal IP address information, which is information about the IPaddress of another node which belongs to a virtual node other than selfvirtual node and about the virtual node to which said IP addressbelongs, and which has been advertised from the node which correspondsto the interface of the other virtual node, and transmitting it toanother node within self virtual node.
 40. A node according to claim 38,further comprising: a means for gathering together and storing IPaddress information from other nodes within self virtual node; a meansfor advertising the IP address information which has been gatheredtogether by this gathering together and storing means to a node whichcorresponds to an interface of another virtual node; a means for storingexternal IP address information, which is information about the IPaddress of another node which belongs to a virtual node other than selfvirtual node and about the virtual node to which said IP addressbelongs, and which has been advertised from the node which correspondsto the interface of the other virtual node; and a means for offering theexternal IP address group information which has been stored in saidstoring means to said other nodes, according to requests from said othernodes.
 41. A node according to claim 38, further comprising: a means forgathering together and storing IP address information from other nodeswithin self virtual node, and link cost information between said othernodes and self node; a means for advertising the IP address informationand link cost information which have been gathered together by thisgathering together and storing means to a node which corresponds to aninterface of another virtual node; and a means for storing external IPaddress information, which is information about the IP address ofanother node which belongs to a virtual node other than self virtualnode and about the virtual node to which said IP address belongs, andwhich has been advertised from the node which corresponds to theinterface of the other virtual node, and link cost information from saidnode which corresponds to the interface of the other virtual node tosaid other node, in correspondence to the IP address of said other node,and transmitting it to another node within self virtual node.
 42. A nodeaccording to claim 38, further comprising: a means for gatheringtogether and storing IP address information from other nodes within selfvirtual node, and link cost information between said other nodes andself node; a means for advertising the IP address information and linkcost information which have been gathered together by this gatheringtogether and storing means to a node which corresponds to an interfaceof another virtual node; a means for storing external IP addressinformation, which is information about the IP address of another nodewhich belongs to a virtual node other than self virtual node and aboutthe virtual node to which said IP address belongs, and which has beenadvertised from the node which corresponds to the interface of the othervirtual node, and link cost information from said node which correspondsto the interface of the other virtual node to said other node, incorrespondence to said IP address of said other node; and a means foroffering the external IP address group information and the link costinformation which have been stored in said storing means to said othernodes, according to requests from said other nodes.
 43. A node accordingto claim 38, further comprising: a means for receiving a packet forchecking reachability from another node within self virtual node; ameans for collecting together IP addresses of packets which have beenreceived by said receiving means and generating internal IP addressgroup information which is related to nodes within self virtual node; ameans for interchanging and harmonizing the internal IP address groupinformation which has been generated by said generating means with othernodes which correspond to said interface within self virtual node andadjusting it appropriately, and synchronizing it as unified internal IPaddress group information for self virtual node; and a means foradvertising this internal IP address group information which has beenunified by said synchronizing means to a node which corresponds to aninterface with an other virtual node.
 44. A node according to claim 38,wherein said advertisement means comprises: a means for deciding whetheror not an advertisement path is present from an other node whichcorresponds to said interface within self virtual node to a node whichcorresponds to an interface with the same other virtual node; and ameans for, when the decision result from said decision means is “yes”,performing advertisement via any advertisement path of self node or ofsaid other node to the node which corresponds to said interface of saidother virtual node.
 45. A node according to claim 38, furthercomprising: a means for receiving a packet for checking reachabilityfrom an other node within self virtual node; a means for summarizing theIP addresses of packets which have been received by said receiving meansand generating internal address group information which is related to anode within self virtual node; and a means for advertising the internalIP address group information which has been generated by said generatingmeans to the node which corresponds to the interface with the othervirtual node.
 46. A node according to claim 38, further comprising: ameans for receiving from an other node within self virtual node a packetfor checking reachability which includes information to the effect thatself node is the one with the n-th cheapest link cost from the point ofview of said other node; a means for summarizing the IP addresses ofpackets which have been received by said receiving means and generatinginternal IP address group information which is related to a node withinself virtual node for each of said n values; and a means for advertisingthe internal IP address group information which has been generated bysaid generating means to the node which corresponds to the interfacewith the other virtual node.
 47. A node which constitutes a virtual nodeof level 1 in a layered network which has been defined by dividing upthe nodes which make up the network into cells each made up from one ora plurality of said nodes and defining these cells as virtual nodes oflevel 1, so that these virtual nodes of level 1 constitute a virtualnetwork of level 1, further dividing up these virtual nodes of level 1which constitute said virtual network of level 1 into cells which areconstituted by one or a plurality of virtual nodes, so as to constitutevirtual nodes of level 2, and constituting a layered network by virtualnetworks of levels 1 through N which have been built up by performingthe process of dividing into cells and making into virtual nodes in thismanner once or a plurality of times, and by, if a link exists in saidlayered network which connects between different virtual nodes of thesame level or of different levels, defining a node which corresponds tothe point of contact between the interior of the virtual node upon thislink and the exterior as an interface, so that, when the highest levelvirtual node to which said interface is related is of level M (whereM≦N), said interface serves as a plurality of hierarchical interfaces oflevel 1 through level N, comprising, if self node itself corresponds tosaid interface: a means for advertising to a node which corresponds toan interface on the same level as self node link information about alink on the same level as self node which has been connected to selfnode and link cost information for said link; and a means for receiving,from a node which corresponds to an interface on the same level withself node, advertisement of link information with a node whichcorresponds to said interface on the same level with self node, and linkcost information for said link, and storing said information.
 48. A nodeaccording to claim 47, further comprising a means for, ahead of pathcomputation, requesting and obtaining, from said node which correspondsto said interface, link information with a node which corresponds to aninterface with the next highest level than self node, and link costinformation for said link.
 49. A node according to any one of claims 27through 29, wherein the source node for path establishment comprises: ameans for specifying a virtual node to which said destination nodebelongs from the IP address of the destination node for pathestablishment, based upon the external IP address group information; anda means for searching for a path to the node which corresponds to theinterface of the virtual node to which said destination node belongswhich has been specified by said specifying means, based upon linkinformation between a node which corresponds to an interface of selfvirtual node, and a node which corresponds to an interface of a virtualnode on level 2 or higher, and link cost information for said link. 50.A node according to claim 49, further comprising: a means for requestingand obtaining, from a node which corresponds to an interface of avirtual node to which said destination node belongs, link informationfor within said virtual node, and link cost information for said link;and a means for searching for, in addition to the path which has beensearched out by said means for searching out a path to a node whichcorresponds to an interface of a virtual node to which said destinationnode belongs, a path to said destination node from said node whichcorresponds to said interface, based upon link information which hasbeen obtained by said requesting and obtaining means, and link costinformation for said link.
 51. A node according to claim 49, furthercomprising: a means for requesting and obtaining, from a node whichcorresponds to an interface of a virtual node which is included in apath from self node to said destination node, link information forwithin said virtual node, and link cost information for said link; and ameans for searching out a path within said virtual node which isincluded in the path from self node to said destination node, based uponsaid link information and said link cost information for said link whichhave been obtained by said requesting and obtaining means.
 52. A nodeaccording to any one of claims 27 through 29, wherein the source nodefor path establishment comprises: a means for specifying a virtual nodeto which said destination node belongs from the IP address of thedestination node for path establishment, based upon the external IPaddress group information; and a means for notifying to the destinationnode to which a path is to be established information which specifies onwhich level is the virtual node of the topmost level for which pathcomputation from self node to the node which corresponds to theinterface is possible based upon information about a link between a nodewhich corresponds to an interface of self virtual node and a node whichcorresponds to an interface of a virtual node of level 2 or greater andlink cost information for said link, and the result of searching for apath from self node to the node which corresponds to said interface forwhich the link cost is the lowest in order up to the n-th lowest; andsaid destination node comprises a means for, along with searching out apath from self node to the node which corresponds to the interface withthe virtual node of said topmost level for which path computation fromsaid source node to the node which corresponds to the interface ispossible based upon said information which has been notified, alsocombining said search results with the results of searching for a pathup to said n-th lowest one, and notifying the path for which the linkcost is the minimum to said source node as the final path which has beenfound.
 53. A node according to any one of claims 27, 36, 38, and 47,further comprising: a means for referring to link information which hasbeen stored in said storing means and deciding whether or not a linkwhich connects self virtual node and an other virtual node is connectedto self node; a means for when, according to the decision result of thisdecision means, a link which connects self virtual node and an othervirtual node is connected to self node, deciding whether or not selfnode corresponds to a termination point for a layer of an LSP which hasbeen established over said link; and a means for when, according to thedecision result of this decision means, self node corresponds to saidtermination point, recognizing that self node is a node whichcorresponds to said interface, and exercising a function whichcorresponds to said interface.
 54. A node according to any one of claims27, 36, 38, and 47, further comprising: a means for observing theresource utilization state related to self node; a means for, if, basedupon the results of observation by this observation means, no room isavailable in the resources which are used for data transmission toanother node within self virtual node and self node corresponds to saidinterface, along with exercising a function as a node which belongs toan other virtual node of level 1 to which self node is connected, alsoupdating information about the virtual node to which self node belongsalong with change of said associated virtual node; a means foradvertising the change of contents of this updating means; and a meansfor, when a said advertisement has been received from an other node,updating the information about the virtual node to which self nodebelongs based upon said advertisement.
 55. A node according to any oneof claims 27, 36, 38, and 47, further comprising: a means for observingthe cost of a link which is related to self node; a means for, if, basedupon the results of observation by this observation means, the link costwhich is used for data transmission to an other node within self virtualnode is greater than a threshold value, and self node corresponds tosaid interface, along with activating a function as a node which belongsto an other virtual node of level 1 to which self node is connected,updating the information about the virtual node to which self nodebelongs along with change of said associated virtual node; a means foradvertising the updated contents which have been updated by thisupdating means; and a means for, when a said advertisement has beenreceived from an other node, updating the information about the virtualnode to which self node belongs based upon said advertisement.
 56. Alayered network comprising a node according to any one of claims 27, 36,38, and
 47. 57. A method for building a layered network according toclaim 56, wherein, when, corresponding to a layer of an LSP which hasbeen established in a link between self virtual node and another virtualnode, a node which is endowed with a function of terminating an LSP ofsaid layer has terminated an LSP of said layer, said node is establishedas a node which corresponds to said interface.
 58. A method for buildinga layered network according to claim 56, wherein, when there is nocapacity in resources which are used for data transmission over linkswhich have been established between nodes, said nodes are separated intodifferent virtual nodes.
 59. A method for building a layered networkaccording to claim 56, wherein when the link cost for data transmissionover links which have been established between nodes has exceeded athreshold value, said nodes are separated into different virtual nodes.60. A network control device which controls the nodes which make up alayered network according to claim 56 all together, comprising a meansfor, when, corresponding to a layer of an LSP which has been establishedin a link between self virtual node and another virtual node, a nodewhich is endowed with a function of terminating an LSP of said layer hasterminated an LSP of said layer, establishing said node as a node whichcorresponds to said interface.
 61. A network control device whichcontrols the nodes which make up a layered network according to claim 56all together, comprising a means for, when there is no vacant capacityin resources which are used for data transmission over links which havebeen established between nodes, dividing up said nodes into differentvirtual nodes.
 62. A network control device which controls the nodeswhich make up a layered network according to claim 56 all together,comprising a means for, when the link cost for data transmission overlinks which have been established between nodes has exceeded a thresholdvalue, dividing up said nodes into different virtual nodes.